Shell Optimax

[danhay]

I know the benefits of this fuel are recognised widely within the PH circle.

I always understood that the higher RON rating meant that it enabled cars with anti knock to run more ignition advance, and therefore a bit more power.

However, I've have felt immediate improvements even in vehicles with carbs and no engine management..so not just down to cleaning of the inlet system?

I'm beginning to suspect that Optimax might have a slightly higher calorific value than normal petrol?

How else could it make non FI vehicles feel faster?

[danhay]

When the car went in for a service, which included a tune up (carbs and distributor) it had ordinary 95 ron unleaded in it. Also, if it was set up for higher octane petrol would it not pink with lower octane stuff in?

[danhay]

VYT said:

In fact, when Optimax first came out there was some comment that it had a lower calorific value than the 95 RON fuel.

That would explain smoother running? I had an Dual fuel car, and that felt smoother, though less quick, when running on LPG which has only about 80% of the calories of petrol.