YZ250

I hesitate to start yet another oil thread as I have read a million of them, too, but here goes.

I want to use an oil that I can easily get at an auto supply, and I would prefer 20W50 synthetic. Around here, everyone carries synthetic up to 10W40. They always carry some dino at 20W50. I change the oil often (every event or two), and the application is track/racing with a little street use (mostly for checking out the car).

So am I better off using 10W40 synthetic or 20W50 dino?

DrZ1

After reading at nausea the 50 page oil thread on the Pelican forum I opted for Swepco 306 15w-40 for street and probably also for the track. I have had problems w/ synthetics in the past. Royal Purple racing oil let down my Ducati 996, and Mobile 1 let me down years back on a high HP 300zxTT. So I dont have much faith in Synthetics. The PO of the 944T reccomended the Cheveron Delo oil and I used that until the formulations appeared to change. I did not want to pay 12-13$ a quart for some of the reccomended motorcycle oils that seem to fit the parameters for our engines. I assumed you were speaking of the car in your avitar.

Steve

M758

20W50 Dino

For a 944 track car heavier is better. BTW.. 15w50 Mobil 1 should be easy to get any place.


Personally I get AMSOIL Series 2000 20w50 by mail order. I order 4 gallons at time. Expensive, but worth it I believe.

Potomac-Greg

Mobil 1 has an extended life oil in 15W50 (as Joe points out). Pretty easy to get.

I go with synthetic out of an abundance of caution. The #2 crank bearing is a known weak point, and maybe there's nothing you can do to preserve it, but maybe synthetic oil will make the difference. As the oil gets older (and closer to a change) I will top up with Castrol GTX in 20W50 flavor.

I used to go with AMSOIL when I was using it in my boat, but then I realized that my boat engines would rust out long before they wore out, so I'm back with dino.

Veloce Raptor

+2 on the Mobil1 15-50.

YZ250

I've read so many posts about Mobil 1 leaking in the older cars that I have completely scratched it from my list. Does that just apply to the lighter weight oils like 5W-40?

Veloce Raptor

Sorry, I dont know. I have never had that problem with M1.

rlm328

Using 20w-50 VR-1. The older engines are not as tight of a tolerance as modern engines ergo the need for larger sized molecules. The synthetics are uniform sized molecules where the dino's moecules are all over the place. The various sized molecules allow for a better gap bridging capability.

Bull

Mobil 1 15-50W here also, and in many cars. I have found that if they are leakers, they will leak, and if they are not, they don't no matter what type of oil if it is the proper viscosity range. I have used M1 in many older engines with no leaks, but they were good, tight engines.

Potomac-Greg

Synthetic seems to leak more/faster than dino, but that's not going to change my mind. As long as most of it stays in, I'm happy.

333pg333

I don't get your logic here. It sounds like a contradiction to me. You're trying to protect against #2 failure yet opting for a lighter synth oil? ZDDP that's all you need to look for. Check your M1 for that.

Potomac-Greg

I don't think it's correct to refer to a synth as "lighter" just because it flows better (more) when cold. When up to operating temp, a 15W40 synthetic is not going to be thinner than a 15W40 dino oil. It's just thinner when it's sitting in the driveway cold.

And ZDDP has been identified as important for non-roller tappet engines, but not for our 2.5s.

It's all folklore, but I feel pretty sure that pouring thick stuff in the top is not necessarily the solution.

Geoffrey

To decide between Dino and Synthetic, I would look at your oil temperatures. If they are below 220, then, when changed often, Dino will work. However, if you regularly run at high oil temperatures, then a Synthetic oil is the better choice.

smlporsche

This in incorrect.
A 15W * oil weather syn or dino will be the same viscosity when it's "sitting in your driveway"

One of the main advantages of a syn oil is its ability to be formulated in a lighter and and wider viscosity range i.e 0W-40 or 15W50.

The vast majority of engine wear comes when you first turn it over. A synthetic with it's lighter cold rating will get to all the engine internals faster than dino and thus severely reduce the amount of metal to metal friction. At least that was the way it was explained to me by the head of R&D for a major oil company...

The lighter the oil range the easier it flows. That is why many pure racing engines (i.e. F1 run very low viscosity oils, something like 0W-10...)

In my car I started running 0W-40 for most of the year and during the hottest months I run 15W-50. So far, so good.

M758

It may, but you are talking about track use.

In my 135k mile 88 944 Turbo S street car I run 20w50 Valvoline VR1. I have some oil leaks (pan gasket I think) and this creats less leakage on the old original seals.

My race motor in 944 NA has been rebuilt so it does not leak a drop and uses synthetic. The worry about synthetic causing leaks is really only for street cars. The reason is that you can get by with marginal seals on a dino oil, but not so with synthics. That is fear. However once you start tracking the car hard you need protection and marginals seals will leak with anyoil. So it is an entirely new ball of wax. You are shooting for max protection and if you have a leak the only answer is to fix it.

My Turbo leaks some oil which not an issue for street use. I would not drive it on track like that since 1) it would leak too much on the track and 2) it make leak to excessive oil consumption wich would lead to spun bearing.