What motor lasts longer

[Katahdin]

I was trying to install the thought that if you run a gas engine at the same design rpms, stroke, etc of a diesel it may last a lot longer than the perception most people have.

Please define "same amount of work."

I'm not biased either way, I have a diesel engine, gas engines, and a multifuel engine that will run on gas or diesel. I just know that the characteristics of each are very different and I need an all-things-equal comparison criteria so I can put my head around it.

 

[Baby Grand]

Everything being equal what motor will last the longest, Diesel or gas???

If displacement & task to be done are equal, then diesel.
There's a reason class 1 & 2 trucks are almost all diesel.
I had the misfortune to drive a gas sheetrock truck many years ago.
20 speed gearbox and no 'nads at all.
It's theme song was "I Love a Parade".
Had to flog the daylights out of it just to crest a gentle hill in low range.
Similar diesel truck we had would almost idle over the same hill in road gear.

 

[ATP]

We had an old gleaner combine f model that had a 262 gas motor...in line 6cyl that ran forever.... never the first issue.....
and 4 diesel tractors that never gave us a engine related problem...
usually... a gas motor works better for varying rpm applications... and the diesels shine at constant rpm apps..(in the field)...

and usually the diesel is more effecient at a given work load...

 

[murphy1244]

Define equal. If stroke, rpm, compression, etc are the same then the characteristics that make a diesel engine last longer no longer give it an edge.....likewise, ramp up a 3000rpm diesel engine up to 6500rpm, or whatever the average small block gas engine runs at, and watch how well the diesel holds together, just don't stand too close!

My gosh we have too many lawyers on this thread. Let me explain equal. As in proper maintenance as per manual. Yea lets run the gas engine the same compression as a diesel.

 

[Verticaltrx]

While generally a diesel will last longer, here are a few things that will increase the longevity of both (things that are being lost in a lot of today's engines):

-bigger displacement for given hp
-bigger bore/shorter stroke
-lower rpm
-inline vs V
-greater oil and cooling capacity
-naturally aspirated

 

[Soundguy]

Equal would be the engine doing the same amount of work.

Why you suggested taking a diesel past its design RPM is mystery to me and does not offer a comparison.

i agree.. and i don't see too many diesel with a 6.5:1 compression ratio either.. so again.. no comparison.

I have plenty of vintage gassers at home.. but I also would have to bet on diesels.

the diesel in my 99 f350 is doing alot better than the gasser in my 2000 gmc yukon or the 98 dodge ram i sold.. and all were at or nearing 200k.. actually my 7.3psd has more miles than the other 2...

 

[Gator6x4]

My gosh we have too many lawyers on this thread. Let me explain equal. As in proper maintenance as per manual. Yea lets run the gas engine the same compression as a diesel.

That is a good answer "murphy1244" We can't find gas that will not spark knock in gas engines running the low compression ratio of today. Increase the compression ratio to 22:1 fill the tank with that wonderfull ethanol blend and tow to the front yard for good "Yard Art" that used to be a motor vehicle and the gasser will last for years and years.

 

[murphy1244]

That is a good answer "murphy1244" We can't find gas that will not spark knock in gas engines running the low compression ratio of today. Increase the compression ratio to 22:1 fill the tank with that wonderfull ethanol blend and tow to the front yard for good "Yard Art" that used to be a motor vehicle and the gasser will last for years and years.

? Did you mean diesel?

 

[Katahdin]

Thanks for clarifying the comparison criteria. Yes, I would agree a diesel typically lasts longer then a gasoline engine per intended applications. The diesel engine has fewer firing cycles and rotations in a given timeframe, so of course it would last longer.

However, I have a 22:1 compression ignition engine that will run on today's gasoline and its 1960s technology. Would love to see a modern production version of it if the EPA allowed.

 

[PILOON]

Shucks, just look at the mileage they get on municipal buses and hi-way rigs! and also note that they do oil changes at unheard of miles.
It seems that oil analysis is a big key to mileage (and other maintenance).
Shucks I have heard of numbers like 200, 250,000 miles and those rigs and buses do shift gears a lot.
But then I gather that the best overall engine is propane powered as it is the cleanest running fuel.