Diesel V8 - or straight six

[Kevin H]

Originally Posted by Janne

Here we have the US style petrol, and I thought I use a 50/50 mix between the Higher Octane and the Lower octane.
What do you recommend?

What is "US style petrol"?

I don't see much point in mixing lower octane (91 RON?) petrol with higher octane (98 RON?), surely you may as well just use one or the other.

I use 98 RON petrol in my 411 S5 but since the engine was rebuilt it has a higher CR. The original Chrysler V8's had a relatively low compression ratio so 91/92 RON petrol should suffice.

The 400 CID engines used in the 411 S4 & S5 actually have a lower CR than the 383s in the earlier 411s.

If you don't drive it very hard then you probably don't need to worry about VSR (valve seat recession), but you could always put in an additive to guard against that.

That said, if the engine number in your car (411 S5?) has a "J" series number (or later) it will have hardened valve seats anyway.

As for the metric vs imperial argument, given that the metric users on this site far outnumber the US Imperial users, I suggest we use litres from now on when discussion fuel prices. Then Lou can use the calculator on his cell phone instead of everyone else