Can I use Mobil 1 oil?

[ChiefPilot]

Originally Posted by bret

ok, please read first post, we all know lead is bad for none dispersant oil, my question is about synthetic oil use with Unleaded fuel. We know the main problem with auto fuel is its low vapor pressure. with EFII a large percent of fuel is being circulated back to tank so the vapor lock problem is greatly reduced. OK, Flame Jacket....ON

So there's potential risks as others have discussed but I haven't read any clear advantages to using Mobile 1. No flames, it's your engine.

[Toobuilder]

I guess the real question here is being lost: what is the mechanism that makes AD oils a requirement in aviation engines? If it is the huge lead content in the fuel, then what if that goes away because you are running unleaded?

I think Bret has a valid question. We all know that things went bad back in the day, but like Bret, I'm also going with EFI (Ross' SDS) and am hoping the Rocket will be happy with auto fuel. It would be nice to know the particulars about the oil behavior because we might have a game changer now. Not that I'm looking to change oil, just curious.

Not trying to be argumentative, but does anyone have any actual data that relates to a Lycoming engine ingesting ONLY unleaded?

[lr172]

There is a lot involved in oil chemistry and it's much more than just AD packages. First, auto oils have been under increasing pressure from the tree huggers for quite some time and modern oils are a compromise with modern engines.

I'll give you an example. Years ago oils had a lot of ZDDP to support high pressure, shear, loads. This was most critical in the cam/lifter interface. By the late 90's, all engines had roller tappets and the oil makers, acting under EPA pressure, cut the ZDDP quantities WAY back to help minimize emissions. The hot rod and classic car guys started eating cams at alarming rates (mostly during break-in, but many failures were in-service). It took several years for people to figure out what was happening. In fairness, a decent percentage of this community was using strong valve springs, but the failures were still very prominent in stock configurations. GM still uses a special additive package in the initial oil fill to accomodate break-in, as the modern oils don't have enough of them to support break-in.

I would not want modern auto oil because it is matched to modern engines and has many compromises in it to specifically fit the current application AND regulatory pressure, at the expense of broad application support. Our aviation oils aren't requlated (API classes) and are engineered for the challenges specifically associated with our engines and that goes beyond just leaded fuel.

EDIT: I would also be worried about anti-scuff additives. Modern engines run tighter Piston/wall clearances and therefore don't need as much scuff protection.

Larry

[jdearborn]

Interesting question Bret. Your logic is very clear.

[Tomcat RV4]

Mike Newall has the best answer , in that, in an antique (lycoming) use appropriate oil. Any one fortunate enough to have a modern engine I believe Mobil 1 is great..I have used in various engine for 15 yrs..I DON'T BELIEVE IN LEAVING OIL IN ANY ENGINE FOREVER! Use common sense with sythetics as far as changes go..Tom

[Raymo]

Great question, Bret. It would seem that there was a reason for going to synthetic back then but was not tested sufficiently.

Lead will be going away in the next couple of years anyway so this topic is sure to return.

[Auburntsts]

If and when 100LL goes away and eliminates the lead issue, my guess will be that an aviation synthetic will be made available (although I bet it won't be Mobil who I would hazard to guess would be a bit gun shy about re-introducing AV-1).

I admit up front I'm no oil expert, but my limited understanding is even if you were using unleaded fuel you wouldn't want to use Mobil 1 in your Lycoming because it's formulated for water cooled engines that have tight tolerances and operating parameters far different from our air cooled engines. Doesn't mean it wouldn't work, but for me and my limited knowledge the risk of an oil related engine issue doesn't justify the usage of an oil formulated for cars. YMMV....

[Toobuilder]

Valid point about the ZDDP issue and its effect on flat tappet camshaft systems. Many of us in the classic car/hot rod world are acutely aware of the problem and have found work arounds. High ZDDP content oils for ?diesel? engines is still available and I know that is an option employed by some. The other is the increasing retrofit of roller camshaft systems to the early engines which eases the pain of reduced ZDDP content. And it is this point which brings this thread back to relevance. Unlike the era of synthetic oil failure in the early 90?s, Lycoming engines have switched to roller cams. So although the basic architecture of the Lycoming is rooted in the ancient times, the materials and internal systems are certainly not.

Automotive oils may still be a bad idea for a current Lycoming, but many of the stated reasons for the early failures are long gone (leaded gas and flat tappets, in particular). It would be nice to discuss the remaining hurdles in an intelligent, technical manner.

[simpkinsona]

Great discussion points presented here. I'll add a data point. Mobile 1 indeed has lowered the level of ZDDP over the last few years, EXCEPT in the 15 w-50 weight. I use this oil in 2aircooled Porsche race cars. I don't see any reason it would not work well in a Lycoming with unleaded fuel.

Of course any time you run something with a small sample size you are taking unknown risks. I have a Subaru engine in my airplane so I know a little about the risk of small population configuration.

-Andy

[rv7charlie]

Interesting that one of the downsides is lack of shear strength (assuming that it actually applies to synthetics) on flat tappet cams. The rotary a/c engine guys using RWS gear drives use synthetic engine oil specifically because it seems to provide smoother, quieter operation of the gearbox (engine oil lubes the plain bearing, and the planetary gearset, in the gearbox).

Charlie