Originally Posted by Augustus

A few points...

Technically, premium gas isn't required in a (stock) Z. Required as in the engine will explode if you don't use it. Per the manual, you can use 87 octane, but it's not recommended and you should avoid "spirited" driving if doing so. Using 87 in a high-compression engine means you'll get more knock. Knock = bad. Now in any modern car, the knock-sensors will detect knock and pull the timing before you even hear it. Retarded timing = less power and likely less MPG. Bad.

In my experience (based on owning several 'premium-recommended' cars over the years and being stuck at some podunk gas station that only had 87 a handful of times), running lower-octane gas in a premium-recommended car is a zero-sum game. It will cost you $3 less to fill up, yes, but you're going to see a decrease in MPG that's >= the cost you saved to fill up.

Bottom line, just put premium in you Z. It's a sports car. If you can't afford premium, buy a different car.



Actually, no, they don't. European/English gas is about the same octane as we have in the US. Like miles vs. kilometers, there is a difference in how octane is presented at the pump. In Canada & Europe, they use the straight "research-octane-number" or "RON". In the US, we use the "AKI" or (R+M/2) measurement. Nitty gritty details can be found elsewhere, but basically..

91/92 octane Euro/UK = 87 octane US
95 octane Euro/UK = 91 octane US
98 octane Euro/UK = 93/94 octane US.

So don't think we have "crappy" gas here in the US because of the octane ratings. It's simply not true. That said, there are some stations in Europe (Shell V-Power?) that sell 100 octane gas, and that equates to like 95 octane in the US, which is a notch better than what we (generally) have here. And it is true that some Euro-spec vehicles may require this, which must be slightly detuned for the US market.

Similarly, it's like how vehicles in the UK seem to get better MPG than they do in the US (for Top Gear UK fans, this is relevant). They actually do get better MPG, but it's not the technology, it's simply the size of the gallon. An imperial gallon is 4.5L whereas a US gallon is 3.8L.