Quote:
Originally Posted by GT182
I don't understand why anyone uses diesel oil on their gas engines. It's for diesel engines not gas. I used it at one time in my 79 Formula and it ruined the engine bearings. That's one of the reasons I only use Valvoline. You might think your doing your engine a big favor but it the long run you aren't. And I've heard that from a number of retailers and those that have used it.
Sorry for the rant but I hojnestly found out the hard way.  |
All that sounds good to the totally uninformed who are unfamiliar with engine and fluid bearing design, but is of course totally false. Diesel oil did not ruin your bearings, nor has it ruined anyone else's.
Diesel engine bearings are no different than gasoline engine bearings, and oil intended for diesel engines is not fundamentally different than oil intended for gasoline engines. There are additive packages that differ somewhat, but they are absolutely interchangeable with no risk of damage. Now, using a high-zinc diesel oil in a modern car with a catalytic converters and sensitive O2 sensors may cause problems with those parts, but it will do no harm whatsoever to the engine itself.
Now, diesel oil is designed for the much harsher environment of a diesel crankcase, and is thus more robust. It also has to deal with more soot contamination and diesel fuel dilution than a gasoline engine oil. The additives and properties that result are beneficial in gasoline engines as well. Conventional diesel oils are not designed for prolonged high RPM, nor prolonged high temperature use, so something like Rotella T would not be suitable in any serious race engine that sees serious track time, but it is absolutely acceptable and in many ways better for everyday road usage.
Your anecdotal story of ruined bearings obviously neglects to mention some other serious factor that was the primary reason for your bearing failures, because the oil wasn't it. So long as you were using the proper viscosity oil of course, and changing it at proper intervals.
My own anecdotal evidence includes using Shell Rotella T 15-W40 extensively in numerous old carbureted pushrod engines over the years, including nearly 50k miles on the already high mileage 455 in my '71. I used nothing but Rotella T in that engine from the moment I acquired it with 193k on the clock. When I tore that engine down at 241k miles, it was still a good runner, had good oil pressure, bearings looked perfectly fine, and I have no doubt it would have continued to run for many tens of thousands more miles. Same goes for numerous other pushrod engines that I have used it in and have put tens of thousands of miles on. Never had any sign of trouble from any of them.
But of course, just like so many things in life, people love to fall back on their one-time singular piece of anecdotal evidence, having done no additional research on the subject, and present it as a definitive argument. Anyone that understands fluid bearing design and has some knowledge of automotive engine oils would never make such a foolish claim that "diesel oil ruined their bearings the one time I used it", because that is of course absurd.
So there, there's a counter-rant. I've been fighting the ridiculous myths about oil for years, but they persist because people love sticking to their anecdotes and blaming someone else, because it's easier than accepting reality sometimes.