I'll explain, after my service last week on 8,000 miles the S came back with my own supply of Mobil 1 Synthetic 0-40W, and any acceleration increase isn't noticeable (obviously, as it seemed in perfect running order before it went in) but I have noticed the following on a few good runs over last weekend.

Changing up from second to third I used to see 63 mph as I was slotting home right on the 'limit', and 93 from third to fourth,
now I'm seeing 65 mph and 95, has my limiter on my UK car shifted from 9200 to ~~~9350??? because of this oil????

Paul

 

Why did you choose 0 w40? Most recommendations I've seen are for 10 w30.

 

Could be due to excessive tire wear at the dealership on their "test drive". No seriously they prob didnt do that but with tire wear you will see a mph or 2 increase as the tire diamiter decreases.

 

Tire wear won't explain the difference if you're just looking at car's speedo. The speedo pickup is on the drivetrain. Tire wear will change (lower) the "actual" speed of the car at a given engine speed, but the speedo reading will remain the same. The only reason I can think of for the higher speed is that the new oil for some reason doesn't allow the rev limiter to limit as well as before. I think that the better lubrication lets the engine run a little faster when the limiter kicks in.

 

so would it be safe to say that using Redline oil instead of mobil 1 could possibly increase that threshold some more? before plucking down the $8/bottle charge on that oil, i'd like to know if it's really worth it.

 

Worth it in terms of protection: arguable yes (can't hurt).
Worth it in terms of performance: no. Once you hit the rev limiter, your already past the point you should have shifted.

 

Sorry did't answer your first question. The threshold doesn't actually change. The rev limiter will still kick in at the same point. But as it does, I think with the better lubrication, the engine doesn't decelerate as fast to get below the threshold. So as the rev limiter kicks in and out, the better lubrigation lets the engine run at a slightly higher "average" engine speed.

 

Just to clarify I'm not hitting the limiter but on a perfect change up just kissing it for a fraction, not long enough to feel it in operation at all.
I'm happy either way, the oil is the grade that I've only seen for Mobil 1 in the UK, in theory it protects in Arctic conditions to desert conditions, and I'm happy with that, seems to warm through even quicker than before the change ( i.e. from departure from Garage to a roundabout ~ 1.5 miles away it hits three bars, before it took 2 miles ,roughly, I can check in tenths of a mile for anyone who is really interested!).

Just a note although I get it cheaper via a source this 0-40W costs ~

 

Why?

 

Just seems like that if you're driving on the rev limiter, you can't accelerate anymore, so then you should shift. I suspect that there are some instances like autocrossing that it may be better to stay on the rev limiter if you'll need to shift back down again very quickly.