synthetic oil vs. petroleum based

The previous owner of my 93 C-2 used a petroleum based motor oil. I would now like to switch to Mobil 1. I understand that all the oil cannot be drained. Any comments would be appreciated.

Mad:

I believe that all synthetics are compatible with pertroleum, so that if you are changing from petro to syn, there is no need to "flush".

However, I have always wondered just exactly what the constituant parts of synthetic motor oil are. Does anyone know exactly what the material is? I have run Mobil-1 now for about 5,000 miles, including track events, and the oil is still "clean and clear". Quite unlike my petroleum-based oils like Kendall GT-1.

What is synthetic made of?.......Andras

I don't know what Mobil 1 is made of, I think must contain gold or something based on the price! with that said I use it in the summer,15w-50 and mineral in the winter. What i'd like to know is just what rocket scientist at porsche designed an oil system that you can't drain out ALL the oil?, doesn't this seem to lead to the conclusion that we'll always have "contaminated" oil in the car?

Wrencher:

Actually the "only" oil that doesn't drain is the small amount that's between the oil tank and the front cooler(s). Everything else does drain out the bottom of both the tank and the sump.

This might be about a quart or so, but it does get "diluted" with eleven (11) new quarts of oil. Since the filters are supposed to filter out all the contaminants, your new 11 quarts of will "over-ride" (great technical term, eh?) the one quart of old. I really don't think you have much to worry about. Besides, I'm not sure how Porsche could have designed the system to drain the oil lines and the cooler to allow your draining, anyway.

Theoretically, you could run the engine after you've drained the sump and the tank, for there should be enough residual oil between surfaces, adhering by surface tension, to allow you to "drain" the lines and the cooler, but I don't recommend that. Easier to just live with the "dilution"......Andras

thanks Andras, just didn't know where that extra qt. was hiding out. I don't believe I'll try anything as risky as running the engine "dry" to get it all out. YIKES! I to have had comments about how clean Mobil 1 stays. even after many miles including track time I still have trouble reading the dipstick because the stuff is so clear. One guy at the track trying to help read the stick said "well if you'd just let your oil get dirty you would'nt have this problem". Yikes again!

There are two types of synthetic motor oils. One type is synthetic hydrocarbon based and another is polyester based. I'm pretty sure that Mobile 1 is polyester based. Polyester is very heat resistant, that is to say heat will not alter its characteristics and viscosity. This makes it very good for use in turbo or other high heat applications. Both types of synthetics are compatable with dino oil, some are sold this way as sythetic "blends".

One of the reasons I use Mobile 1 is it's high temp capability (i'm hoping this also means flash point?) my car leaks from the cam shaft seal to power steering and it drips right down onto the header. Yea, I know fix the leak, but this fix does'nt come cheap, so for its Mobil 1 and a fire extinguisher. call me crazy

The "dirty oil" you are referring to is not the result of the petro hydrocarbons breaking down (you can't see that) but the cantaminants present after formulation. It is too expensive for the oil companies to remove all of the sulfur and unsaturated bi-products. It also, ironically, is a good indicator of condensation or fuel contamination - these turn oil contaminants black quickly. I used Mobile-1 in my V8 S10 for many years until my driving habbits changed. I now only drive 1 mile to work so fuel washing and condensation are a real issue. The oil must be changed frequently to get rid of these contaminants, synthetics are not needed under these circumstances.

About 2,000 miles ago I switched to Mobil 1 tri-synthetic for my 3.2 L 911. The main thing I've noticed is that since the flashpoint is so high on synthetics, there is no burn anymore compared to the cheap petroleum based oil I used before where I had to add a little oil every month or so.

I also understand that gas mileage has been know to greatly improve with the Mobil 1 synthetic (or probably any synthetic) I'm still not sure about this since I keep testing the synthetic oil by maintaining pretty high RPM's. I calculated 19mpg on my last fill and I was averaging a little less than that before.

Since you can go about twice as long between oil changes, and there may be gas mileage benefits, I think it's worth it.

------------------
Zach
77 911S 3.2

The main reasons to use synthetic oils are their ability to lubricate with a wider range of temps and their ability to withstand higher heat ranges. When I use the A/C and see the needle heading towards the upper white line on the temp gauge, with Mobil 1 I no longer worry.

With petro based oils when you go much over 240 or so you are asking for problems. I have used syn oils both in Europe and here for almost 15 years and they are excellent replacements, however do seep a bit more if your engine is not totally tight. It is cheap insurance for your very expensive engine!

I just change my oil yesterday, (Castrol 5W50 Syntec) and used 10 and 1/2 quarts for refill. What is the total capacity in quarts?

Have you checked out the Pelican Parts
Tech Articles ?? There is an article on
making sense of synthetic lubricants and
one on all about motor oils, these are located near the bottom of the articles list