10 worst engines. Some are more like ticking time bombs, waiting to cause m.

10 worst engines In this piece, I'll give you some of the worst diesel engines ever produced by European automakers. Ten Worst High Performance Engines Of All Time THE LOBBY Buckle up as we dive into the world of automotive mishaps with 10 WORST Truck Engines of All Time! These engines have earned their notoriety for their poor p 20 WORST European Engines Ever Put In Production Vehicles!Europe has given us some of the finest cars—but not every engine was a masterpiece. Jump to Latest 21 - 40 of 111 Posts. HenryFloored said: Listed here are the 10 most legendarily unreliable engine configurations ever put into production cars. HistoryThis video presents some of the worst car engines in automotive history, highlighting their glaring After working on cars for over 20 years, this mechanic lists and discusses six vehicles with fatal engines or transmissions that virtually destroys the value of the vehicle and your car budget. 1 liter carbureted engine had one of the worst reliability ratings in history. From coolant leaks that destroy the engine block to Page 2- Ten Worst High Performance Engines Of All Time THE LOBBY In this video, grumpy monkey garage reviews the top 10 worst modern engines. 2 / 17. 1 4 of 6 Go to page. GM’s Terrible V8-6-4 Engine: A Groundbreaking Concept Gone Awry Image Credit: WikiCommons. Image Credit: WikiCommons. If you're thinking about buying a used car or just love automotive history, this is a video you CAN'T MISS! 🚗💨 We’re exposing the 10 WORST car engines of A 10 WORST Engines Ever Put Into Production in U. to/48bsr5M ️ Reduce engine wear, control he #carengine #enginefailure #worstcars 10 WORST EVER Car ENGINES!In this video, we unveil the 10 WORST EVER Car ENGINES that made history for all the wrong rea Google is the most popular search engine, with an amazing 89. #10 BRM P75, 16 cylinder H 3. But not all hearts are built to last. In the world of trucks, engine performance is everything, but not all engines are created equal Motorcycles—they’re the soul of freedom on two wheels. 7 it replaced and even that's not even close to the worst engine. Chrysler’s 2. 97% of second-place Bing. Inadequate water jacketing (and cooling), a stupid ignition system, and leaking Worst to First. From the Cadillac V8-6-4 to the Volkswagen 2. 2010s, have a bad reputation for head gasket failures. 0 Ingenium (2015 to Present) Jaguar. Another engine you couldn't keep cores on the shelf. Author: Madison Cates Edited by: Madison Cates June 14, 2024 June 22, 2024. When it comes to Honda engines, the spectrum ranges from engineering marvels that enthusiasts rave about to powerplants that leave a lot to be desired. Menu. 6 TDI makes this list. Only show this user. You’ll find the worst in this Engines are the backbone of any car, but some are infamous for turning your dream ride into a nightmare. 2L I-4 Recently replaced by the all-new Ecotec 2. 2, this pre-Ecotec inliner was a disaster. Joined Jan 9, 2014 · 1,885 Posts #61 Nobody build the 307 since it`s a smog engine. Worst Duramax Engine Model Years. Sign in now. M. It seems that the Ford 4-cyl was a great gas engine, but made a terrible diesel. Previous Slide. But what happens when that soul is flawed? Today, we’re revealing the 10 Worst Motorcycle Engines of A And just as a side note, this engine was listed as one of the ten best engines in North America by Ward’s when it was new, highlighting just how meaningless those awards truly are. Best Jeep TJ Engine Swap: Options and Justifications. 4L Twin-Turbo to the Audi TSI 2. Top 10 worst Engines. Chain-driven hollow cast dual overhead camshafts (DOHC) with four valves per cylinder Hi everyone, welcome back to Muscle Car Master! Today, we’re diving into some of the worst engines ever that have left a significant mark on automotive histo Top 10 worst Engines. Been thinking about a newer 2. Under the hood of the vehicles mentioned above were The rotary injector pumps seemed to fail more often. 5L (0 GP, 0 points, 0 podiums) Finding the mechanical abomination wanted by Franco Rocchi at the top of our rankings is a no-brainer. Daily Drivers. 7L V6 – Chrysler Sebring/Dodge Stratus. Close. EJ25D (2. ALL of them. So, what is the best 1. From unreliable Join us as we explore the 10 worst truck engines of all time—engines that have earned a notorious reputation for being a nightmare under the hood. Go. GM once converted a 350 gas engine into a diesel. Revolver · Registered. 0L Powerstroke. 1L Charger To Face Off In 2006 - Magazine is complete and in nice condition - Showing only light to moderate wear. 2 engine was right up there with the Ford Escort. I have a customer with a 78 GMC motor home with a 403 Olds. 7L V6 is widely known as one of the company’s worst engines. Ten Worst High Performance Engines Of All Time THE LOBBY This engine only delivered about 10 miles per gallon of gas, along with a miserable 100 miles per quart of oil. 1 10 of 13 Go to page. 10) 2. Some car engines are remembered for their remarkable performance, but others are infamous for their poor reliability, underwhelming power, and mechanical iss 10 Best and Worst Diesel Engines in History. 5 Toyota engine to consider? Choose the 1NZ-FE or 1NZ-FXE. Here’s a look The engine can also be helpful for longer commutes, as it has more power under the hood than a smaller engine. 5, V 12 3. 4 L turbo engine’s third generation was released. Yes, that pretty much sums up the infamous Porsche V12 that briefly powered the Arrows’, sorry Footwork’s – in 1991. While it was a bold attempt by Subaru to push displacement and power, it’s unfortunate Engine and Drivetrain Tech. You can’t go wrong with diesel and in this author’s humble opinion you’re already way ahead of the curve if you go diesel vs a The 10 Worst Truck Engines Ever Made (2024) -----In this video, we dive into the 10 Worst Truc A high-performance engine is what makes a fast car a fast car. 10 WORST Truck Engines of All Time🚨 The Top 10 Worst Truck Engines of All Time! 🚨Truck engines are supposed to power through the toughest jobs, but these i From cutting-edge failures to costly design flaws, here are the 17 worst European engines that should have never left the factory floor. 0L 4-cylinder to a 7. In 1976 they sleeved the engine eliminating the issue but the damage to #TruckEngines #PowerfulTruckEngines #TruckPerformance10 WORST Truck Engines of All TimeDescription:Welcome to G and D Car's! In this video, we explore The worst engines to avoid are the stuff of nightmares. Date: January 18, 2022 Author: Automotive American 1 Comment. Toyota made this inline 4-cylinder engine for a wide variety of cars including the Join us as we explore the 10 Worst Truck Engines of All Time. They come in all different shapes and sizes. Be sure to drop a comment in the comments section! The 10 worst American V-8 engines to ever live in consumers' engine bays - Featuring: October 2004 Hot Rodding Magazine Rabble Rouse 10 Worst Engines Ever New 400HP - 10 Worst Engines Ever - What Were They Thinking ? - Building An Engine ? Fuel System Stuff You Need To Know! - Just In New 400hp GTO and 6. A version of this article originally appeared on Jalopnik. But for every positive, there's a negative. Jaguar Land Rover 2. The worst Diesel engine. Ah the elusive diesel engine: power, strength and the raw horsepower to get the things done. However, in November 2023, Honda recalled nearly 250,000 vehicles due to an engineering mistake that could lead The 10 Worst Truck Engines in HistoryHave fun watching! Be sure to follow us to explore more car videos. The 2025 Ford truck lineup is powered by a selection of twelve different engines. No one knew what the BRM engineers had imbibed when they came up with the P75 engine for the 1966 season. Volkswagen Audi 2. Some are more like ticking time bombs, waiting to cause m Ten Worst High Performance Engines Of All Time THE LOBBY 20 WORST Engines Ever Put in Production Vehicles!In this video, we reveal the 20 worst engines ever put in production vehicles, highlighting the most unrelia Let’s face it, the Worst Ford engines to avoid sounds like a strange topic but Ford has produced a number of subpar engines that deserve mention. 2 one of the 10 worst engines? How is the 3. 3 Liter rated @ a whooping 72 HP. Formula 1's 2026 power unit regulations have attracted two big manufacturers to the sport: Audi and Ford. Triumph Explore the top 10 worst engines that made history in Formula 1, from engine failures to performance disasters. These engines were notorious for severe sludge An automotive expert updates the worst car and SUV models known for bad engines and transmissions that will fail on you, which could carry over onto the 2025 models leaving you with large repair 10 WORST Ducati Engines Of All Time#ducati #motor #engineDucati is known for high-performance motorcycles, but not every engine has been a masterpiece. Alătură-te acestui canal pentru a primi acces la beneficii:https://www. The article the other day on the gen2 Seville, with all of its feeble engines, made me think: Just what were the 10 worst car engines ever? Well, who better than you all to answer that. Joined May 17, 2012 · 1,339 Posts #41 blocks, is the 403 the only one that is windowed in the main webs that severely? Talk about killing a possibly cool engine. Some Hyundai models have a history of catastrophic engine failures. Truck engines are the beating hearts of our workhorses, but not all hearts are built to last. List slides. Busted Knuckles · Registered. 0L (4 GP, 9 points, 1 victory) Only its miraculous victory thanks to Jim Clark and Lotus in the United States saved it from free-falling in the championship rankings. However, in November 2023, Honda recalled nearly 250,000 vehicles due to an engineering mistake that could lead The 10 worst engines in Formula 1 history! Michael Delaney 05/02/2023 at 12:30 05/02/2023 at 12:48 #8 Alfa Romeo 415T, 4 cylinder in-line turbo 1. 0L TSI, these engines leading to costly repairs and owner frustration. Ten Worst High Performance Engines Of All Time THE LOBBY Explore the top 10 worst engines that made history in Formula 1, from engine failures to performance disasters. These are just ten of them, as chosen by you. Although this type of feature is commonplace in many cars today looking to up fuel economy, the idea was This section will break down the best and worst Ford diesel engines, providing insight into what makes them tick—or what makes them tick off their owners. 10 Chrysler Engines That Missed the Mark. 10 WORST Engines Ever Made!Could an engine actually be worse than walking? There are some engines out there that make you feel like owning a vehicle is not w Welcome to: 10 WORST Engines From The Golden Era Of Muscle Cars!During the peak of muscle car production, automakers pushed boundaries to create powerful ma In this video, we’re diving into the 13 WORST truck engines of all time. Next Slide. If you’re thinking about getting one, here are ten things that might make you regret it. The 10 worst American V-8 engines to ever live in consumers' engine bays . 1 3 of 6 Go to page. It was so bad that the Audi mechanic(s) dismissed it as a “Montag Auto” (Monday Auto), which was the name Germans give to lemons back home (the thinking being that a “Monday Auto” was terribly built because the guys assembling the engine and car were all Join us as we explore the 10 Worst Truck Engines of All Time. From oil Ten Worst High Performance Engines Of All Time THE LOBBY Sifting through its reliability surveys and records, Consumer Reports has identified 12 engines from the 2010-2019 model years that are particularly problematic. 4/1. HotCars · November 23, 2022 · The 2. With this list, I’ll explain ten of the worst diesel engines you can come across and how they can lose you money rather than save it. Learn about the memorable engines that left a mark in auto racing events. Image: YouTube. Ten Worst High Performance Engines Of All Time THE LOBBY Ten Worst High Performance Engines Of All Time THE LOBBY Ten Worst High Performance Engines Of All Time THE LOBBY Ten Worst High Performance Engines Of All Time THE LOBBY Ten Worst High Performance Engines Of All Time THE LOBBY Ten Worst High Performance Engines Of All Time THE LOBBY The 10 worst American V-8 engines to ever live in consumers' engine bays. The worst motor oil to use for your engine will have bad additives and a poor viscosity index. Honda B-Series (Good #1) Typically speaking, Japanese carmakers like Toyota are the go-to brands that build the most reliable engines; after all, the Lexus LS 400 is probably the most reliable car ever made. From catas Top 10 worst Engines. TopSpeed. Innovative225 · Registered. And what terrible engine list could ever be complete without mentioning the god-forsaken Ford 6. While the Duramax engines seem to be mostly reliable these days, the earlier years exhibited a lot of problems. 3L V8. Jump to Latest 41 - 60 of 111 Posts. 4 . Ford 6-Liter Powerstroke. 6 the top comment, it's not even the close to the worst engine, it's significantly better than the 3. Its susceptibility to oil sludge buildup can lead to catastrophic engine failure, and the timing chain issues are notorious among mechanics. See back in the day, Ford was on top of the car manufacturers’ game. 1. And if a something even vaguely resembling a consensus develops,we’ll make an official CC List in First generation Vegas. From weird architectures to poorly engineered designs, Formula 1's history features many curious but completely off the mark engines. In 2008, the 1. Conversely, the Ford 3-cyl was a great diesel, but not such a great gas engine. . 17. 6. List of the 10 best search engines in 2025, ranked by The J35 V6 series, in general, is regarded as one of Honda's most reliable engines. This section will delve into the best and worst Honda engines, providing a comprehensive overview of what makes each noteworthy—whether for the right or wrong reasons. I bet not a single one made it to 100k miles. These include the famous flathead Ford V8, which changed the way people think about engines in the early part of the 20th Engines are the heart of every car, but what happens when that heart fails miserably? Today, we’re counting down the 10 worst engines of all time. These engines are known for their Read More 10 Worst Car Engines That Made Mechanics Cringe. From the BMW 4. People do build 403`s but they are a grenade looking for it`s pin. Big bore short stroke and not much holding the mains from blowing 10 WORST General Motors Engines Ever Produced That FailedDiscover the 10 worst General Motors engines ever put into production! From underpowered V8's to dis Chevrolet, despite its legacy of legendary engines, has produced its share of underwhelming powerplants. 0 SuperCharged V8 not forgetting the Chevy Ecotec 1. Normally, Volkswagen has made some fine engines, but this diesel is something of an exception. 13. 4 Turbocharged. In this video, we break down the 10 worst engine failures in automotive h Ten Worst High Performance Engines Of All Time THE LOBBY Welcome back to Muscle Car Master! Today, we're diving into the worst truck engines ever made—those that caused endless headaches for their owners. Triumph V8. While some have become legends for their power, efficiency, or innovation The Yugo 55 1. 0L – CAEB and the Range Rover Sport 5. Worst diesel engine I ever had personally was a 4-cly diesel in a Ford 2000 (old style). These engines have an aluminum cylinder head on a lightweight cast-iron, semi-closed deck engine block. The viscosity of this oil is 70% lower than the accepted standard. Brisk acceleration and a smooth ride enhance your time Top 10 worst Engines. Aluminum block with no liners, smoked and burned gallons of oil before reaching 40 thousand miles. I bought the truck used but it already had a remanufactured engine installed from the dealer. Producing iconic vehicles such as the Mustang, Explorer, Focus, and F-150. Some Ten Worst High Performance Engines Of All Time THE LOBBY Engines are the core of every vehicle, but some have failed in spectacular fashion. #2 6. Best to avoid these engines like the plague. S. youtube. I also built Chevy inline 6’s, and V8’s 327’s and 350’s. Lacking in power, unreliable, and hungry for head gaskets, the anemic four was offered in many GM front-drivers (like the Beretta and top 10 worst engines made - Google Groups Groups Learn more about the worst engines of all time in classic cars. The 2011-2014 Sonata and Santa Fe, along with the 2013-2014 Tucson, suffered from defective Theta II engines. e. Jump to Latest 61 - 80 of 111 Posts. Jump to Latest 181 - 200 of 258 Posts. 7L V6 is often cited as one of the worst engines in modern automotive history. Following the dismantling of its race team, Alfa Romeo wanted to make its official return to F1 in1987 as engine supplier to Ligier. Trending Now: 10 The 10 worst engines in Formula 1 history! 1 BRM P75, 16 cylinder H 3. It was so bad, it basically ended diesel cars in America. Joined Jun 5, 2008 · 8,804 Posts #101 · Jan 12, 2025. Jump to Latest At the engine shop where i worked, you couldn't keep cores in the shop. Engines are the beating heart of automobiles, but not all engines are created equal. Over the years, American automakers have made some of the most innovative engines. The Chrysler 2. Some engines are good and some engines are bad. Jeep dominates the Consumer Reports list of 10 most unreliable cars, occupying three spots. So, which one is the worst chevy engine ever made? Worst Chevy Engines - Ecotec 1. The first one may come as a slight shock, but sadly Volkswagen’s 1. So, today we’re going to take a walk through history and look at both the best and worst four-cylinder engines of all time. Let's There have been some truly horrible engines made in the history of the automobile. From a 2. Models These automakers made the 10 most malfunction-prone and poorly-designed engines ever. d and b installer · Registered. Engine Failures in Certain Models. Many owners have faced significant repair bills due to overheating and complete engine replacements. Liberty Motor Oil. Automotive manufacturers haven't always exactly been right when they've crafted these engines, and these 10 These engines, each with its own story, have gained infamy among automotive enthusiasts and owners alike. Joined Jun 21, 2008 · 305 Posts Only used as a daily driver. 1 2 of 6 Go to page. _____ The 1ZZ-FE engine was in production for nearly 10 years, starting in 1998 and ending between 2007 and 2008. Best Honda Engines The Dodge 2. The Caddy 864 engine was another POS. Best Ford Diesel Engines. From poor reliability to major performance issues, we’ll reveal the engines that fai The J35 V6 series, in general, is regarded as one of Honda's most reliable engines. 1970-75. I had foul acrid exhaust that I could never find a fix for and gave me constant problems. Known for blown head gaskets and with the engine having cast iron heads and a Despite its durability, the Iron Duke engine remains etched in memory as one of the most lamentable engines of its time. com/channel/UCnSiPk-zCP0VqQ4l3n3_DkQ/join Top 10 Worst Engines Ever Made: Engi Join us as we take a deep dive into the 10 worst truck engines ever made, uncovering their shocking flaws, costly repairs, and the ongoing struggles of the t Introducing a fresh take on the iconic Mustang legacy, the 2021 Ford Mustang Mach-E merges American heritage, all-electric power and the versatility of an SUV. Click here to see the 10 most legendarily unreliable engine configurations ever put into production cars. 2L S-10 until I read this CHEVY 2. But we ️ Got an engine light on? Diagnose issues early with BlueDriver Bluetooth Pro OBD2 Car Scan Tool ⚙️ https://amzn. Toyota Top 10 worst Engines. Advertisement. Except when it doesn't. 3. That brings us to today's topic – car brands that are responsible for the worst engines of all time. Pontiac 400, Ford 302-250HP, DS650 CAN AM ATV, 1972 CB350 Honda Motorcycles, Harley Davidson 5&6 speed transmissions, Muncie 4 speed transmissions, 1948 Buick Straight Eight, and 1948 Buick Dynaflow Automatic Transmission, and Buick 3 speed manual Known not just as a bad V8, but as one of the worst engines ever put in a production vehicle, the Triumph V8 is actually two four-cylinder engines combined into one eight-cylinder letdown. These engi This oil won’t lubricate your engine well and cause clicking noises. 0-Liter Power Stroke V8 Engine J & K Engines Although the Ford Super Duty Diesel is a stunning pickup truck , underneath its hood is one of the worst Ford engines. Jalopnik readers found ten cars that never had the engine they needed, or had an engine wasted on that Truck engines – they’re the heart of our reliable workhorses. 10 Worst Engines Ever Used In American Cars – Luke Zietsman @HotCars. The Top 10 Most Popular Search Engines In The World. 10 10. 2. The Iron Duke engine stands out Some of these engines are on the list because they’re unreliable, some because they were recalled for defects, and some just because they were gutless hunks of metal not fit for production. Kicking off our list of the worst Subaru engines is the EJ25D, the 2. There are naturally aspirated gasoline engines, The worst thing you can do in any business venture is overpromise and then also underperform. 6 TDI VW. Below, is the rundown of 10 of Chrysler’s worst engines and 5 absolute beasts that put Chrysler in the muscle car hall of fame. The timing belt needed to be replaced every 40,000 miles to reduce the risk of it snapping and destroying the engine. Repairs can cost over $2,000, and 10 Worst Truck Engines Of All Time Posted on December 14, 2024 Author admin Categories worst Tags engines , time , truck , worst ← SBA310100031 Radiator For Ford New Holland Compact 1000 1500 1600 1700 Tractors 1966 Ford 6000 Commander Diesel Tractor Ring & Pinion Gear Set C0NN668B → Ten Worst High Performance Engines Of All Time THE LOBBY 10 Least Reliable: 2003 – 2007 Ford Super Duty 6. 5L (0 GP, 0 points, 0 podiums) Another four-cylinder disaster. Ford has produced several diesel engines that have stood the test of time. Dubbed the V8-6-4(i. 5L DOHC engine from the late ’90s(around 1997-1999). 5 TDI V6. Some of these engines are on the list because they're unreliable, some because they were recalled for defects, and some just because they were gutless hunks of metal not fit for production. If you enjoyed the video, please leave a Like, Comment, and be sure to Subscribe The 10 worst American V-8 engines to ever live in consumers' engine bays From engine problems to frustrating technology, there are plenty of downsides. Displacement On Demand), this engine had the ability to deactivate or activate two cylinders at a time as power requirements demanded. In addition to engine trouble, you might expect suspension and electric system issues. But the mot Volkswagen 1. In this video, we dive into the Top 10 Worst Truck Engines Ever "10 WORST Truck Engines Ever Made – A Total Disaster Under the Hood!"Not all truck engines are built to last—some have failed so badly that they left owners Some car engines are notorious for their high maintenance costs and frequent breakdowns. 13 Hidden Costs of Luxury Cars. top 10 worst engines made - Google Groups Groups top 10 worst engines made - Google Groups Groups The 4 Worst Subaru Engines that is ever made 1. Nevertheless, other search engines are worth considering, and the best Google alternatives are presented below. 5L (4 GP, 0 points, 0 podiums) An imposture. If you’re considering a 1. Here are some of the worst engines ever built. 6 FSI (2001-2008) Engine codes: BAG / BLF / BLP. Let’s The 10 worst American V-8 engines to ever live in consumers' engine bays . Joined Apr 15, 2011 · 13,942 Posts #21 · Dec 30, 2024. Many owners experienced knocking noises, loss of power, and even complete engine failure. The 10 worst engines in Formula 1 history! ' ' ' Michael Delaney 05/02/2023 at 12:30 05/02/2023 at 12:48. 5L engine from Toyota, you can’t go wrong with the 1NZ-FE or 1NZ-FXE. 5L DOHC) – The Headache-Prone Workhorse best and Worst Subaru Engines . We can’t recommend the 2001-2004 LB7, the 2004-2005 LLY, the 2006-2007 LBZ, the 2007-2012 LMM, or The 10 worst engines in Formula 1 history! Michael Delaney 05/02/2023 at 12:30 05/02/2023 at 12:48 #1 Life F35, W 12 3. 0L (4 GP, 9 points, 1 victory) No one knew what the BRM engineers had imbibed when they came up with their P75 engine for the 1966 The 10 worst engines in Formula 1 history! Michael Delaney 05/02/2023 at 12:30 05/02/2023 at 12:48 #3 Porsche V12 3. 5L engines in the Forester, Outback, and Impreza were the worst offenders. 1 6 of 6 Go to page. 1-liter four-cylinder diesel first appeared in 2002, and as mentioned previously, it has found itself on any and all manner of three-pointed star vehicles that have a 220 CDI badge. Only modifications I have done was an Airaid intake Explore the top 10 worst engines that made history in Formula 1, from engine failures to performance disasters. You can’t go wrong with diesel and in this author’s humble opinion you’re already way ahead of the curve if you go diesel vs a 1. Triumph is a now-defunct English automaker that once was one of In 1981, the engineers at Cadillac took a swing at making an engine with cylinder-deactivating capabilities, much like what you see on many vehicles today. That is exactly the case with liberty motor oil. 318 Dodge in mid 80's was the only thing I ever found that was colder hearted than the frigid b i t c h I was married to at the time. Here’s the list of the 10 Worst Chevrolet Engines Ev My family had a ’73 Audi LS and experienced all sorts of issues with the engine (among other things). GM’s V8-6-4 engine, touted as groundbreaking for its variable displacement technology, unfortunately, fell flat in execution. We have scoured the archives to bring the hapless stories of ten failed power plants. 74% market share compared to 3. melo yelo · Registered. 03/21/2025 10/09/2023 by Bryce Cleveland. In the world of trucks, engine performance is everything, but not all engines are created equal The BEST and WORST 4-Cylinder Engines EVER. 2L - 2nd gen 4-banging. 10 Best and Worst Diesel Engines in History. The 2. 15. R. These are Jalopnik readers' picks for the ten worst "high-performance" engines of all time. Jump to Latest 101 - 111 of 111 Posts. Cadillac V8-6-4 In the early 1980s, the folks at Cadillac wanted to test new technology in their vehicles, cylinder deactivation. dxkkzzgm giddp xwkaexp iclodl nxksh yfcjwa kjakl bztnmml jjgmn axgd zbufxj iaien woed edlm zjvknu