Lizard1

recently, when I took my wife's BMW in for service, the service advisor noted that there was alot of carbon buildup and asked if we had been using supreme(93 octane)? car is 18 mos old with 14K miles.

we had been using 93 octane from Chevron and he stated that BMW is now recommending ~90 octane b/c the higher octanes are causing alot of carbon buildup and throwing codes

can this really be true? are we in reality hurting our Porsche engines by running higher octanes?

Kiko

Not really... actually your 03' BMW will adjust ignition timing to the fuel and, the more advanced the timing is the cleaner it burns meaning less carbon build up which is nothing more than "leftovers" of the quimical reaction. The reason for that carbon build up which might be perfectly normal (how did he come to that conclusion? Did he take the head off? - I find it hard to believe) is that probably your wife drives very slowly using only the lower rev range where the combustion is far from perfect due to valve timing and low in-chamber temperatures or uses the car for short trips where the fuel ratio is overly rich. by the way the most effective rev range is near maximum torque.

1999Porsche911

Adviser is just showing his ignorance and confirming that most service advisers know little about the cars they service.

Torags

That's sounds more like the right answer. In the days of lead gas, that was a normal problem for performance cars. You had to (blow them out) run to high rpms. 60-70's Jags could never seem to run right in cities.

P-Car fanatic

Basically she needs to redline it every gear for a couple of days!!!!!!!