1984 GMC 6.2 with Mobil 1 10W-30

The "different" sound is most likely your emagination. :)

>

When I read this one, I had to laugh. So many people believe all the unfounded rumors about switching between Dino oil and synthetic that it's hard to know what the truth is.

I've switched back and forth numerous times on several vehicles and it hasn't hurt any of them. I've experienced no catastrophic engine failure, no parts flying helter skelter and nothing going up in smoke (go figure). BTW, when detergent oils were first introduced, the U.S. Army switched all their vehicles over to the new oil with no problems attributable to the new oil (that's a lot of vehicles).

Synthetics have been used by the military for decades (most notably in jet engines) and have performed exceptionally well. The only difference between the first synthetics and the new ones is that the older ones ate neoprene seals and caused leaks to develop whereas the new oils don't do that. Incidentally, the reason these oils worked in jet engines is because they used different seals like spring-loaded carbon and non-neoprene compounds.

Mobil 1 is one of the best (and possibly the best) synthetic oil on the market. As long as a synthetic oil meets or exceeds the specifications of the engine manufacturer, you can use it safely.

I was under the assumption that there is sometimes a sludge that is helping seal some of the gaskets, that when the detergent synth comes in cleans it up and then leaks. But then again I would think a good ole' oil flush would do that too?

~KJ~

Well is cranks easier because you are using 10w oil rather then 15w oil. The only concern I would have is that it does not have the soot control and anti-foaming additives that diesel oil does. As long as the oil is diesel certified you probably will not have any problems. Can't comment on the change in sound because the 6.2 I have, has a totally mechanical injection system. As far a 219k being hi-mileage... well mine has over 400k miles and does not burn or blow a drop of oil. So take care of it and it will last longer then the rest of the truck. :-)

mark

Hi!

At first I thought so. Ya know, being pleased about changing the oil and not having any disasters besides a bad tire I figured that I was just hearing things.

But...it isn't. The starter is definitely turning the engine over faster than it ever did before in bitterly cold weather and the engine sounds different both at idle and when accelerating.

William The Guesser

Hi!

Not quite the reaction I'd been looking for...

I didn't expect a massive failure of anything. I know that's not really likely to happen. But I also know that this truck and engine have seen better times and I didn't exclude the possibility however faint of leaks occuring that would be annoying or possibly out of my ability at this time to repair.

William The Guesser

*Snip*

I was concerned about the same thing. I'm not sure that Mobil 1 is compatible with diesels. In fact, I've been told that it's not compatible. If you wanted to run a synthetic in your diesel, it would be better to run Shell Rotella Synthetic 5W40. You get the benefits of synthetic, with the additives your diesel needs. Not only that, but Wal-Mart sells it here for $12 a gallon.

CJ

Hi!

I've always been using 10W-30 oil. That's what the owner's manual says to use for my climate area.

Bottle says it's OK to use in a Diesel, so I am using it.

Yeah, I'd like to see 400K+ from this one as well. So far it is just getting broken in... :-) I do believe it is blowing some oil however.

And...while the engine is still running great, it is coming ever closer to outlasting the truck body. A complete restoration of the body is planned and is proceeding extremely slowly.

William The Guesser

Hi!

compatible.

Well, the bottle said it was OK... I have no idea if it is the best, but it has been a few days now with fair use and nothing has broken yet. In fact, I'd say it's been wonderful. The biggest change of all has been not killing the batteries to get the old truck started.

5W40? (!) Is that a good idea? It isn't listed in the owner's manual that I know of...

William The Guesser

I guess that I must be luckier than some of you (who was it that said "The more I practice, the luckier I get?"). If you have an engine that is "gunked up" then I would definately not use an oil flush in it. If, howevr, you engine has only normal depsits, it probably won't hurt. As for detergent oil, you're confusing the detergent-dispersant in motor oil with laundry detergent. The "detergent" in motor oil is there to keep in suspension, the particles that accumulate in the oil and to prevent them from "plating out" onto the surfaces of the engine (it's then called sludge, gunk, etc.). It is not a cleaning agent like a solvent.

Engine flush, however, IS a cleaning agent and if not used correctly, can destroy your engine. If you put an engine flush or cooling system flush into your engine and then take off for a long drive, enjoy the drive because it will probably cost you a lot of money. All the flushes that I've ever seen have a time limit on using them (usually 5 to 15 minutes at idle) and all of them tell you not to drive the vehicle with the flushing agent in it. I know of one guy that blew his engine by driving 100 miles with an oil system flush in the crankcase (now that was just plain stupid).

Every vehicle that I've used flushes and Synthetic oil in had 100,000+ miles on them when it was done and none of them developed problems. But, this is another one of those things that if it makes you uncomfortable or you're a little unsure - DON'T DO IT. You'll sleep a lot better.

*snip* *snip*

Better watch that; it'll start fouling spark plugs. :-P

CJ

Hay! If you have fouled spark plugs on a diesel engine I would like to see you replace them.... Actually older diesel tractors (1910-1930+) did actually have spark plugs. They would start on kerosene and convert to diesel once warmed up.

mark

Ya but willy runs pure kerosene in his monster. Billows black smog from his rip-roarin starts. He leaves little black flakes that hang in the sky wherever he goes. :-)

-The Lonely Grease Monkey

1985' K5 305CUI TH700R4 NP208 KJ's successor

"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson

Hi!

Yeah, I'll change those right after I work on the muffler belt. :-D

I do think some glow plugs need attention though...

William

Hi!

Dunno if you're referring to me or not....but nope, it's straight Diesel. IIRC the owner's manual said kerosene was a bad bad thing to do??

Someday I want to run WVO in the thing, just to see it happen and to see if it really does smell like frying things when it runs...trouble is that it's costly and will almost certainly require lots of diddling around.

As for rip-roarin' starts, it's always blue smoke when the old truck first lights off from having sat and cooled completely down...but only for an instant or two.

William