6 cylinders versus 4 (longevity)

I thought I adequately explained this. However, I will be happy to explain again.

With all other factors being equal, a six cylinder engine will weigh more than a four cylinder engine. That extra weight will make the six cylinder engine work harder too. So the lower weight of the four cylinder means it doesn’t have to work as hard.

So your assumption (like many assumptions) isn’t based on anything but an unsupported supposition. If I am wrong and you have some kind of proof, please show it.

To whom are you responding? I hope it didn’t take you three posts to respond to one of mine. If so, I hope this conversation doesn’t continue to expand.

Really, if you are witholding some kind of proof, please feel free to share it. I eagerly await it.

I suppose if we were talking about an undersized underdesigned Ford Escort engine from the 1980s, it would seem to be working harder, but with today’s lighter four cylinder cars and better four cylinder engines, the engine is so much lighter that it negates this “overworking” you envision.

Cars are not the same as people but a 150 hp engine has to work harder than a 200 hp engine going up a hill. Harder on valves and bearings.

Whitey: How much more power would it take to push an extra 100#? You yourself said that you doubted if a 3000# car would notice the extra 70# weight. When you come up with “proof” I will search a little more.

Turbo’s just add more power to a given engine, not greater efficiency. They are still sometimes claimed to be efficiency adders (Ford’s eco-boost for example), but that claim only works if you compare the turbo engine to the larger engine that would be required if not for the turbo.

I was responding to you, Whitey. I don’t see you presenting any proof of your assumptions. You talk about lighter and better 4 cylinder engines, don’t you think that 6 cylinder engines have been inproved ofer the years?

“The 6-Cyl report lower “Drive System” Reliability (still average but not above like the 4-Cyl). I would assume that this is the case because the more powerful 6-Cyl can potentially put more stress on the drive system. Interestingly enough the stats for the transmission do not vary (although the 4-Cyl’s still is still a little ahead when it comes to reliablty).”

If the engineers are doing their job the drive trains will be “matched”. Having said that, I stand on my previous statements.

A more powerful engine usually has a greater stipulated performance envelope. If the weaker engine stays within it’s, and the more powerful one the same…longevity should be equivalent. Try to ask a weaker motor to perform in the realm of a motor with greater torque esp., you’re asking for shorter working life…this applies to the other components as well. This also assumes they are both from the same manufacturer with the same design philosophy.

It’s true with all the heavy equipment I’ve operated, it’s true with cars and trucks. If you want a break down, ask a piece of equipment to do something it wasn’t designed to do. Cars and trucks are just equipment designed to perform certain tasks; no more, no less.

You just repeated what I have been saying in several posts. (ask a weaker motor to perform in the realm of a motor with greater torque esp. you are asking for shorter life). Thank you!!

You just repeated what I have been saying in several posts. (ask a weaker motor to perform in the realm of a motor with greater torque esp. you are asking for shorter life).

…But that wasn’t your original position. If that was what you were saying all along, I would have agreed with you. You said a four cylinder engine won’t last as long as a six cylinder engine, which just isn’t true.

What are the most reliable vehicles on the road? In no particular order, they are the Honda Civic (which is only sold with four cylinders), the Honda Accord (most of which are sold with four cylinders), the Toyota Corolla (which is only sold with four cylinders), and the Toyota Camry (most of which are sold with four cylinders).

Having four cylinders doesn’t necessarily make an engine weaker than a six cylinder engine. Engine displacement and other factors are more important than the number of cylinders. Just look at motorcycles for evidence. A 750cc four cylinder engine is weaker than a twin cylinder 1,200cc engine. Displacement is MUCH more important than the number of cylinders.

Is this evidence enough proof for you or do you still need more?

I agree that asking a small engine to do the work of a big engine will shorten its life, but your assumption that this is being asked of cars with four cylinder engines is a faulty assumption. That is where we disagree.

By the way, dagosa also supported my arguement when he said:

A more powerful engine usually has a greater stipulated performance envelope. If the weaker engine stays within it’s, and the more powerful one the same…longevity should be equivalent.

Let’s not cherry pick supporting statements from other people’s posts to make our points. If we can’t make our own points in this debate, the least we can do is not drag others in and claim they support our positions.

Back in the 1950’s, there was this belief that a V-8 engine would outlast an inline 6 cylinder engine. One factor was that most V-8 engines had a shorter stroke than did the inline 6 cylinder engines. Of course, other factors entered in such as final drive ratio. Consumer Reports used to publish a statistic that was piston travel per mile in top gear. In those days, the big concern was piston ring life. The Borg-Warner overdrive was a popular accessory in many cars to give a higher gear ratio. With the improvement in metallurgy, piston travel per mile probably doesn’t mean as much. Ring jobs really aren’t common today as they were in the 1950’s. This may be where the myth started that more cylinders mean less wear.

If you plan to “abuse” the engine, that is fast accelerations and high rpm driving, I would recommend getting the 4 cylinder. In my personal experience I have found that 4 cylinders can take a lot more abuse than a 6.

I guess we were here before…

Depending on how it is driven, a 4-cylinder can last as long (or longer) as any other engine. (Look at all the 200,000 plus mile 4-cylinder Toyota’s and Honda’s out there and still going strong). True, a 4-cylinder motor does rev faster, and sometimes needs to work a little harder, with proper care and maintenance, it can have a very, very long life.

That turbo is going to cost you big time when it fails, and they always do. Get the normally aspirated V-6.

This will be my last comment on this subject, not because I cannot compete with you but because you can’t even understand the facts. A 4 that is asked to carry the same car that a 6 does will not last as long because it will be under more stress. Anyone should be able to see that. MSRRY CHRISTMAS!!!

…I guess that could be true…if you ignore the weight of the engines…and all the other differences between four cylinder cars and six cylinder cars.

If you take a closer look at cars that are available with a four cylinder engine and a six cylinder engine (like the Honda Accord or the Toyota Camry, for example), you will find there are differences other than the engine size. The six cylinder versions will probably have larger, more powerful brakes. They will have different transmissions. They will have different cooling and electrical systems. The six cylinder engines will have larger batteries. There will also be other subtle differences, like the oil, coolant, and transmission fluid capacities. The six cylinder engine will have a larger radiator and maybe larger wheels. So when Honda and Toyota make four cylinder and six cylinder versions of common models, they don’t just replace a six cylinder engine with a four cylinder engine. That would be plain stupid, because in that case, you would be correct. So innovative car manufacturers are careful to make sure the car used with a six cylinder engine doesn’t just get an engine swap. The four cylinder car would have to be lighter in order to maintain an acceptable power to weight ratio.

Even if you go all the way back to the 1980s and look at the third generation Ford Mustang, you will notice the different engines came in different bodies.

Take a closer look at the six cylinder Accord and the four cylinder Accord and you will notice that the engine cylinder count is not the only difference between the two cars. Oh and MSRRY CHRISTMAS to you too. I also hope you have a merry Christmas!

My two cents: Driven in the same manner, a normally aspirated 6 cylinder will probably outlive a 4 cylinder in the same car. However, the difference in longevity is so insignficant and so far down the road that it probably is not worth mentioning. When I was shopping for a Dodge Caravan years ago, I test drove two 2001 models, one with the 3.8 V6, one with the 3.3 V6. The horsepower of these engines were fairly close, but the 3.8 had a lot more torque and it was noticeable when driving. The 3.8 van would shift gears at 2500 rpms while the weaker 3.3 would change gears at 3000+ rpms to get the same acceleration. Obviously, the 3.3 V6 was working harder to get the same result. It probably has a shorter lifespan than the more muscular 3.8, but this difference would probably occur long after these vans were hanging from the electro-magnet at the scrapyard anyway.

No one is mentioning torque. Torque is probably more important than horsepower when considering longevity and power delivery. A 4 cylinder engine and 6 cylinder engine may accelerate similarily, but the 6 will do so with less effort if it produces a lot of torque. My Mazda Tribute has a 3.0 V6 (Ford Duratec) and it does not tow my snowmobile trailer any easier than my aforementioned 2001 Caravan with the 3.3 V6, despite having 20 more hp and weighing 500 lbs. LESS. Why? Torque! The Duratec is a high rpm motor that makes maximum torque at 5000 rpm, while the traditional push-rod Dodge 3.3 makes its torque at a much lower rpm, meaning its power is utilized more efficiently than the multi-valve Ford V6. Generally speaking, the large displacement engine = greater torque at a low rpm. Torque is twisting power, like muscle. A thin, fast runner can outrun a stocky, powerful NFL lineman in a race. But put 200 lbs. of weight on them and race them. The stocky NFL player represents a high torque, lower horsepower engine while the thin runner represents a high horsepower, low torque engine.

As for the extra weight of a 6 cyl. engine increasing the weight because of its extra cylinders, therefore eliminating a power advantage, I respectfully disagree. The weight and power differences are not proportional. The extra power a 6 clyinder provides far exceeds its own weight disadvantage. Just like driving at 60 mph may get you 30 mpg, driving at 70 mph might only get you 25 miles per gallon. Shouldn’t the extra speed make up for the lost mpg? No. For example, the wind resistance increases far more than the speed increase allows for in efficiently.

i read somewhere once that a straight 6 is a very tough engine,the audi is a v6,so im not sure about that.in the uk audi/vw cars are only average for reliability/longivity.so if it was me,id get a bmw 325,with that awesome 2.5 litre straight 6!which should run forever!

Consumer Reports rated the old A4 rather poorly after 5 years, especially the engine, cooling, electrical and power equipment systems. This was for both the I4 and V6, though the I4 is worse. Including in non-engine things; this has everything to do with parts quality and nothing to do with number of cylinders or driving style or engine load. Maybe after 20 years but not 5. Based on engine and cooling problems, I’d guess head gasket failure. The I4 probably has more heat from the turbo. So if the new A4 I4 has a turbo then the non-turbo v6 on that one is probably a better as well. Other brands have 4 cylinder engines (and other sizes) that are much more reliable than both of Audi’s engines. You might want to consider buying a new Audi every few years regardless of the engine or switching brands.

CR rates the BMW 3 series with better reliability than the A4, including excellent engine reliability, but overall its reliability is still around average. Probably the most reliable option among European makes, though.

"I agree that asking a small engine to do the work of a big engine will shorten its life, but your assumption that this is being asked of cars with four cylinder engines is a faulty assumption. That is where we disagree."
It’s not faulty though. If the car owner drives somewhere that is very hilly, tows, or drives very fast, they could be running a 4 up near it’s maximum HP rating for extended lengths of time (well, not the kind of 4 in this Audi probably!). A lot of engines have a continuous HP rating (for industrial use) which is much lower than the rating it’s given in a car. The intension of this is to run at peak HP for short periods of time, and spend most of the time at or below the continuous HP rating. The 6 in this case would not be up near it’s rated HP, while a 4 could. Something like the Toyota 1.6, they put that in a van where normal driving involves mashing it to the floor, and they last forever. But some engines are just not like this, they would indeed prematurely fail after lots of heavy-throttle use.

 A V6 version of most cars does add bigger brakes, maybe suspension upgrades, etc.  This DOESN'T add much weight though.  It's typical for a V6 to have 50% more horsepower than the 4, and it could add under 10% to the weight.  The weight of a V6 car doesn't counterbalance this.

 I don't think people are arguing that in the Audi this would happen, but just saying in general this is the logic of favoring a V6.  In most cases, you would not get into the "bad" range on a 4 or a 6 though.

 I would go for the turbo, BTW.  It's more complicated than a V6, but if you travel anywhere which involves mountain climbing, etc., the turbo will cover for the usual loss of power associated with high altitude.