Engine Lifetime Mileage

Will an 8 cylinder engine last longer than a 6 or 4 cylinder engine? I have 200,000 miles on my Durango and was going to replace it with something that gets better gas mileage.

Wait, you’re replacing the whole car, or you want to swap a 6 or 4 cylinder into your Durango?

Longevity of an engine is more dependent on build quality than number of cylinders. Realistically, almost all cars today have engines that can last a very long time if properly maintained - it’s the other stuff on the car that will crap out before the engine does.

Fuel cost is only one component of total lifetime per-mile cost. Depreciation, taxes, maintenance, insurance, financing, etc. can outweigh a few extra MPG. It also depends upon how many miles you drive. Did you put on 200k miles in three years or in 20?

Number of cylinders doesn’t matter, it’s the care taken of those cylinders, as Shadowfax said. The only issue would be if you get a small engine and ask too much of it (towing, hauling, etc.).

The number of cylinders in an engine is totally irrelevant to its longevity. Design goals, quality of design, build quality, driving environment, and maintenance are the primary determinants.

To offer extreme examples, the Toyota 22RE 4-banger was one of the most durable engines ever put on the road, but there are some V8 engines that have become known for chronic problems including piston slap, blowing headgaskets, and blowing manifold gaskets. There are also 4-bangers that have become known for headgasket problems, such as some from Saturn and Subaru, yet the old smallblock V8 engines (283s, 327s, 260s, 289s) were some of the most durable engines in their eras.

The number of cylinders can no longer be considered the determinant of mileage either. With so many new variations of hybrid coming out, and with so many V6 engines being so close in size to I4 engines, and with so many technology variations like variable cam timing and variable cylinder management, it’s a crap shoot.

My suggestion would be to get a Consumer Reports New Car Preview at the locall bookstore. While not a perfect predicter, it’s IMHO the best collection of reliability statisitics and aut information available. Test drive all those that look good to you.

IF AND ONLY IF the 8 cylinder and 6 cylinder are designed and manufactured and maintained the exact same way then the 8 cylinder will probably last longer. But find me those two engines first.

Not if I use the V8 to get out of the tollbooths faster…

You need to add at least one more qualification - If they are both used in the exact same way and are providing the same amount of power.

If they’re providing the same amount of power and designed with “sameness” as a goal, that would suggest that the displacement is the same. If that’s true, and for the sake of “sameness” than the cylinders in the V8 would have to be 1/3 larger bore. Which means that pistons, heads, connecting rods, valves, cranks, and everything else is different. That makes them totally different engines.

So, the point comes back to the fact that you can’t really say which will last longer because there are too many variables, and that can’t really be changed.

That’s true…

Yup. The second you make the two engines different you’ve added too many variables.

Number of cylinders really has nothing to do with how long an engine, or vehicle, will last. Timely maintenance and repairs have everything to do with longevity. Timely maintenance and repairs even have more to do with longevity and reliability than the badge on the hood. A well maintained Chevy Cavalier will easily outlast a poorly maintained Honda Civic. Congratulations on getting 200k miles out of what many people consider to be a piece of junk (a domestic vehicle). Many consider the 200k mile mark to be attainable only by Japanese cars. Regardless of what you replace your Durango with, proper maintenance and timely repairs will ensure longevity. Before you replace this vehicle, though, put some thought into why you are replacing it. Unless you do a tremendous amount of driving, say, 50k miles a year, it is difficult to see any real-world financial gains by replacing a vehicle only to get better gas mileage, especially if you own your Durango and will be taking on a monthly car payment and possibly higher insurance premiums. All your money saved on fuel, and then some, will be going towards a car payment, insurance, and maybe even more maintenance and repairs than you currently put into your Durango. You may want to consider a more compelling reason to replace this vehicle than lousy gas mileage. Do you have a better reason, or is this it?

A (properly maintained) modern engine (that is not “beat on” on a regular basis) will most likely outlast the original purchaser’s desire to drive the vehicle it is attached to.

In any event, it should last 200K miles…and if you’re still “in love” with whatever you buy at that point, just budget 2c/mile for engine replacement and you’ll be able to afford a professionally-rebuilt engine! (It’s not as if a worn-out engine necessitates scrapping the vehicle.)

P.S. as much as the EPA get bashed in automotive circles, I think that EPA “longevity requirements” have a lot to do with the outstanding engine longevity today, by mandating a minimum level of quality necessary to meet EPA standards that has the side-effect of producing a long-lasting engine.

Mark 9207 has it right.

Good information by all who have post. Let me add that for years, I put too much emphasis on the longevity of my “motors” to the detriment of the rest of the car. Body maintenance and motor mechanics are of at least equal importance. Compare the price of reclaiming a car’s body after years of neglect to replacing a motor. Not only isn’t the car safe, but it maybe “un-inspectable” in those states that still do it.

With this in mind, I believe I can easily make any 4 cylinder car functional for many more miles than the neglected body of any well cared for v8. Regardless of doing engine repair, I’ll always be ahead of the game economically and in safety.

“meanjoe” makes excellent points too about the EPA requirements making cars more long lasting. These requirements certainly put a damper on the Midas Muffler business.

No, but I have not done engine durability testing either.

“These requirements certainly put a damper on the Midas Muffler business.”

I’m not so sure about that. “P0420 Catalyst System Efficiency Below Threshold” seems to have become a part of our daily lexicon.

Thanks for the reply. I also have a 2001 Suburban with 194,000 miles on it. The kids have moved out of the house and we are just looking to down-size when it makes sense. As a side note my most recent memorable experience with the non-domestic vehicle (1998 Toyota 4runner) was when a fire broke out in the engine compartment as my son was pulling into a parking lot at his school. The Toyota dealer said that oil had leaked from the valve cover (bad gasket), dripped onto the starter and created a short which started the fire. The car has 140,000 miles on it and is running well at this time. I reserve judgment on the “domestic vs. Japanese” question for now.

Back in the 1940’s, most engines were inline engines and had a long stroke. When Oldsmobile and Cadillac introduced the short stroke overhead valve V-8 engines in 1949, these engines, under the same conditions, did last longer than the common inline 6. However, in the early 1960’s, the inline 6 cylinder engines were redesigned with shorter stokes which leveled the playing field.
Also, the metallurgy has improved since this time period. Hence, the length of the stroke probably doesn’t make much diffence today. I remember that Consumer Reports used to list a statistic called piston travel per mile. The shorter stroke engine, usually combined with a higher gear ratio, meant less piston ring wear and longer engine life. Consumer Reports no longer reports this statistic as it is meaningless in today’s cars.