Chris Baus

SM Oil reformulations

I've been spending too much time screwing around with my Porsche this spring. If you tend to get obsessive (as I do) I don't recommend buying a 30 year old Porsche, because there are so many things to obsess about on these cars that you soon won't be able to think about anything else (although that turns out to be a good thing for me right now).

I want to mention one thing I found generally interesting. In reading up on routine maintenance for the car, I discovered most major motor oils have been reformulated (with the intent of lowering emissions) this year. Charles Navarro has a lot of information on this here.

The conclusion is new SM rated oils contain significantly less Zinc and Phosphorus to improve the longevity of catalytic converters (at the cost of engine longevity). Unfortunately most older engines require these additives to reduce metal on metal contact. Not to mention my 33 year old car doesn't even have a cat.

So the next you pick up your favorite brand of oil this year, it may have nothing in common with the oil you used at your last change. For instance Mobil 1 15w-50 is a commonly used Porsche oil, but the new formulation is not recommended for air cooled Porsche engines, and it is really easy to miss this.

Another interesting point is that a lot of Porsche owners and engine builders swear by HDEO (Heavy Duty Engine Oil) which is basically truck fleet oil which is sold cheaply in gallon jugs. Shell Rotella T Synthetic 5W-40 can be had for around $16 a gallon. Mineral based oils can be had for half that price. HDEO is formulated for both gasoline and diesel engines to run for extended periods between changes (so mixed diesel/gas fleets need only one oil). Unfortunately some of these oils have been reformulated as well to deal with lower sulfur diesel fuels. In other words, it is a real PITA to find appropriate oil for an air cooled Porsche.

I found some of last year's Shell Rotella T 15W40 HDEO and bought enough for a few changes. Each oil change in a Porsche takes around 2 1/2 gallons of oil, and it is within specs to burn a quart per 1000 miles. When that is gone I will probably use a synthetic HDEO oil. Same stuff farmers in Iowa use in their John Deeres. At $16 a gallon it is hard to justify $10+ a quart for Mobil 1 V Twin 20w-50.

Here's a picture of the car running a new stainless steel exhaust and diesel oil. Easy to obsess about. .