humpty wrote:Higher Octane = Cooler running.... And I have never run additives either...
no no!
As octane gets greater, the Hotter in fact it actually runs.
the burn is slower, and more 'heat' energy is released. if the octane is high enough, the burning fuel would actually still be in the burning process whilst passing through the exhaust valve and manifold, resulting in burnt valves and a dramatic increase in engine bay temperature.
{NOTE: this is not a back fire as the 'ignition' for this burning mixture took place in the combustion chamber, however is finishing up in the exhaust manifold)
(practically the complete opposite of detonation/pinging from 'too low' octane which obviously you don't want from too low octane otherwise it ain't half obvious that internal pressures are going to go off the charts).
I speak from a VERY nasty experience after running a combo of 98 octane and 4 point nulon racing octane booster. (yes stupid but it was an experience to get the most hp by advancing the ignition as much as possible with the higher octane to increase the ability to advance the timing without any pinging). mind you that was ONE VERY nasty cruise. overheating is never fun.
People have established that unleaded fuel is vw friendly. if it pings at 91 octane, check that timing is not too advanced and properly timed. if it is, then go 95 octane. but there is no need to jump to 98 if 95 isn't pinging. It will run hotter with no hp benefits, unless you advance the ignition timing by feel to keep the 'mixture burn' in that combustion chamber.
and you would probably squeeze a couple more hp by advancing so as the higher octane contains the greater energy. I doubt 98 would cause any damage though, but let it be out there that it will definitely not run cooler with a higher octane.
It may or may not pose any damaging threats, but if 95 works, why risk unless certain?
