[Jameel]

So I've had my '83SC since April 14, 2016. In that amount of time I've used many quarts of oil. 14.5 in fact. I've driven the car 4940 miles. I've enjoyed every minute of them. Well, I should say that some family members drive the car too (that landed my older brother in a speeding ticket class, for which I will relish ribbing him forever for) but 95% of those miles are mine. Doing the math, I've got 340 miles per quart avg. since I took ownership. Always Castrol GTX 20w-50.

I've checked mileage and oil consumption since I bought the car. The worse "mileage" I've got was right when I bought the car. Drove it home about 400 miles and it drank up a quart in the first 218 miles. That gave me heartburn the whole way home. I don't think the PO drove the car so much (but his records show good maintenance) so about 1000 miles into my ownership it just kept getting better. The next time I put oil in I got 423 miles per quart. Then it went back down as I drove the car on shorter, 20 mile or so drives, around 300 miles/qt.

Went up to Road America this summer for the vintage races (about 4.5 hour drive) and put oil in before leaving. After driving up to Elkhart and then down to Milwaukee (300+ miles) it needed oil again. So I put in 1.5 quarts (always to halfway between the dots) of a different oil since the station didn't have Castrol. I used Valvoline VR-1 Racing 20w-50. Next time I added oil after the VR-1, I did the math. The VR-1 yielded 686 miles per quart. I was shocked when I checked this. To test my theory I put Castrol back in twice since then (4.5 qts) and my consumption has dropped back to around 280 or less.

So I've got two possible variables. First, the PO sent along a gallon jug of Castrol when I bought the car. I would fill the car from this jug and monitor the level from the little window on the side of the jug. Not exactly sure how accurate these are. So those early numbers might be off. Second, my odometer. For that past 1000 miles or so I've noticed the speedo won't move until I get to 30-35mph. It stays stuck at launch, then jumps to 30 or so when I get to that speed. If I take off, then tap once on the glass (I thought that only worked in movies!) the needle will come to life. My concern here is that I don't always tap the glass, or simply forget. I'm wondering if the odometer is somehow related to this, such that it perhaps doesn't come to life either until I hit a certain speed. I'll admit I don't really know the internals of the mechanism. So if my odo is registering less than my actual mileage, then perhaps my oil consumption is much less than I've calculated.

The car does not smoke, save for the occasional puff at startup. It doens't not leave a smoke trail at heavy throttle. I have not examined the plugs for oil. But the PO had the plugs and wires changed right before I bought the car, and the mechanic (a big Porsche dealership) didn't note anything. In other words, there are no obvious signs of oil consumption that I've seen. I get dollar-size drip on the garage floor if the car sits for several days. If I drive it every day, pretty much no drips in the garage.

I'm actually not paranoid, just curious more or less. I bought the car figuring I'd be doing a top end at some point, so news of that won't be a huge shock or anything.

So, aside from switching over to VR-1 when I do an oil change next, you all have any thoughts?