Can I use Mobil 1 synthetic motor oil

[Shakadula]

Can I use Mobil 1 synthetic motor oil in my GS 400 with rope seals. I just had the motor rebuild and didn't have any leaks for about 1000 miles and after changing the oil to Mobil 1, I have a slight leak that appears to be coming from the rear seal. I'll know for sure whan I change back to regular 10/W30 but am looking for your experience. I've heard it both ways. Synthetic oil is a bad idea and it doesn't matter. Please help.

[Reatta Man]

People that badmouth synthetic oils don't know what they are talking about. Consider this:

1. ALL Corvettes come from the factory with Mobil 1 in them. WHY would Chevy pay the extra money for synthetic oil in these engines, when many other V-8s come with regular oil? Because they know WHY their owners bought the cars and HOW they intend to drive them. What does that tell you?

2. MOST high-priced foreign cars come with all synthetic fluids, including the oil. This includes cars like BMW, Mercedes and others. These manufacturers would NEVER risk having to pay for replacing these engines under warranty and loose thousands of dollars if synthetic oil could possibly damage them. They are using synthetic oil for a reason; it saves THEM money! It's cheap insurance for them.

3. There are NO accounts of mechanics taking high-mileage engines apart that have been on synthetic oil all their life (with proper maintenance) and finding hardened carbon or heavy sludge. You can do all the maintenance you are supposed to do and still develop excess sludge on regular oil. If you don't believe it, I had the owner of a large shop here in San Antonio tell me about a deliver truck with 200,000 miles on it that they do all the maintenance on and the engine has never been taken apart, and uses no oil. 200,000+ miles, uses no oil, still runs strong, never been rebuilt...hmmmmmmmm.......

4. ALL turbine engines (U.S. Air Force, major airlines) run only with synthetic oil in them. Right now, Royal Purple has the Air Force contract. I know; I have seen the Royal Purple boxes come in to the maintenance squadron. Next time the contract comes up, it could be Mobil 1 or AMSOIL. Why? Because all quality synthetic oil meets all, and I mean ALL MILSPEC requirements for turbine engines. Royal Purple, Mobile 1, Castrol, AMSOIL and other national quality brands are all about neck and neck on quality. And they are all light years ahead of regular motor oils. (I know there is somebody out there that is growling and saying right now , "ah, that +&*^%$ idiot doesn't know what he is talking about." I've seen one of these guys demand to have straight 30W only put in his 2003 Dodge pickup. He will be rebuilding his engine in about 60,000 miles and wonder why it wore out so soon.)

If your seals are showing leakage, try going to a synthetic blend oil for a few oil changes, then go to all synthetic again.

Ignore the rumors and stories about synthetic oil that start of with "I know a guy who knows a guy who works at an oil company and he told him......" or "somebody told me years ago that....."

Joe

[2seater]

The synthetics do seem to have a better wicking ability, and the rope seals don't run as "dry" as the more modern rubber lip seals. When synthetics first became common, there was a lot of talk about engines becoming leakers because of it. Sealing technology has improved and I suspect there may have been some changes to the makeup of the synthetics to reduce this tendency, but for my money, synthetics are far superior by any test standard. Does the engine really need it? That argument has gone on since synthetics became common, and it really depends on you. I do run Mobil 1 in all my cars and truck, and I can attest to how clean the engine stays inside, but mostly it's just because the synthetics are the best stuff out there, and that goes for the transmission and differential too. A small leak may be the result, but my $0.02 says it is worth it.

[Reatta Man]

If 2seater isn't careful using Mobil 1, he will end up with a car with 300,000 mile s on it and still running great. Being in Wisconsin, that means the body and frame may rust into oblivion, but the engine will still run great.....

[Shakadula]

Thanks all. I will try the synthetic blend oil for a few oil changes, then go to all synthetic again.

[NTX5467]

Wicking ability has no real bearing on whether the oil is synthetic or not. Case in point, several years ago a friend put Castrol GTX in his engine and then comnplained about the oil leaks. When he got through cussing the Castrol, he went back to Pennzoil and the leaks stopped.

Having used Castrol in all of my engines, all of which were in used cars, I knew that it did not leak out any worse than other oils did. I asked my machine shop associate about that. His comment was that the Castrol was getting into places that the Pennzoil was not, hence the Castrol "found" the gaskets/seals that were prone to leak--wicking ability--whereas the Pennzoil did not.

I concur, modern oils are much better than the were even 10 years ago. The specs keep getting tougher and the designation letters keep getting deeper into the alphabet. Lots of foreign manufacturer requirements too--not to mention "turbo" compatibility.

Synthetic oils can offer longer life than non-synthetic oils, but you didn't hear those longevity claims in the earlier days of synthetic oil advertising. My machine shop associate did mention a Chevy small block that a customer brought in for a rebuild. 100,000+ miles on Amsoil with 3000 mile changes and it still had good hone marks on the cylinder walls. Back then, it was more about extended change intervals than 300K mile engines. Yet the manufacturers never did "bite" for the extended change intervals the synthetics claimed they could do (but with THEIR different synthetic-rated oil filter, which looked like it was more old rags than filter media). So, if you wanted you engine covered by the factory warranty, you had to use the petroleum-based oil change intervals.

Other than wear issues, one main area in the synthetic portfolio is decreased power consumption and better flow at all temperatures. In modern times, this can relate to more power at the flywheel and better EPA economy numbers. Plus, if you have a $50K Corvette or Cadillac, you can afford the extra money for "spec" synthetic oil.

At one point in time, even Valvoline did not recommend their synthetic oil in pre-'85 (or thereabouts) engines. Why? Seal compatibility, most probably.

In reality, the oil's viscosity has little to do with engine longevity. Multi-weights might flow sooner upon startup, but that little issue is not going to wear an engine out in 60,000 miles--period. It didn't do that even in the 1970s! It's more about maintenance for the way the vehicle's driven.

In a modern engine, getting the oil flowing as soon and as easily as possible helps get the engine through the emissions-critical start-up period a little quicker so the computer can go into feedback mode sooner for ultimately decreased emissions AND better fuel economy. That's been the driving force behind multi-weights and synthetics more than getting an engine to last 300K+ miles. We've had many engines come through our shop with over 200K miles and they've used nothing but normal 10W30 oil in them, but with quality oil filters.

I highly suspect the reason that Royal Purple is the current vendor for the military contracts mentioned has more to do with price than anything else. The Government, Ford, GM, or whoever sets the specs and then puts those specs out for bids. You know the rest of the story . . . Not to say that Royal Purple is not a good product, but it's probably more about efficient use of the taxpayer's money. Might even be part of some bid strategy to use local area vendors too.

As for the rope seal seep, I concur that trying blended synthetic oil might be a good move for diagnostic purposes. Even going back to basic oil might be the next step. But do NOT think that using petroleum oil will keep you engine from cratering before 100K miles as, after putting over 350K miles with only petroleum oil (20W50), with decent maintenance, it's more about maintenance than the viscosity of the oil--from my observations--so long as the vistosity is not too high for the application.

Remember when 50W racing motor oil was common? Reason you don't see that any more is that it was determined that it took more power to run the oil pump with that weight of oil in the engine--unless it was a race motor that had lots of fuel dilution that needed to start at 50W to keep the motor alive.

Remember in the 1960s? An engine that had 100K on it was "worn out". Wasn't because specifically of petroleum oils, it was the quality of the oils and the related oil filters. Since that time, both have improved markedly! Even the totally worst oil today is probably better than the best oil of the early 1960s.

And then there's the additive package that makes up the oil. All kinds of friction modifiers that can be in there too--petroleum or synthetic.

In reality, use the best oil you can afford AND works with your engine combination. Then, use a quality oil filter of at least OEM spec quality, but beware of those "premium" filters that have been sold. Lots more cost for little benefit. Even the basic ACDelco Duraguard filter is better than ACDelco filters were in the 1990s, with respect to smaller micron ratings. Then, determine which viscosity rating meets the factory specs and the way you use the engine, but usually 10W30 or 10W40 can be the best compromise. Even 30 weight oil can be the best oil in some applications, temperature ranges, and engines. The fact that modern manufacturers might not recommend straight weight 30 motor oil has more to do with getting their engines past emissions and fuel economy tests. What they use as the "spec oil" in those test/certification engines has to be what they recommend the customer use in their vehicles.

GM's declining to recommend 20W50 oil came in the later '70s or early '80s. The service bulletin mentioned "viscosity improver buildup behind the oil rings" as the reason. Loss of oil control could mean increased emissions, typically. I knew that wasn't happening in my car, but the Pennzoil rep said that GM tested all oils and they found a few that did cause that problem, hence the declining to recommend that viscosity of oil. In reality, it could have had something to do with fuel economy ratings too (more power to run the oil pump = more fuel used to do it). Many side issues!

Just some thoughts,

NTX5467