Gas ?

[grognon]

Hi

I have a Lexus RX400h 2007, i was wonderring wich grade of gas to use when it is hot or cold outside.

When it gets colder, is it better to use more regular or to put super?

Same when it is very hot hotside.

Thanks!

[cduluk]

Well, the "idea" is that a higher grade gas (89,91,93) won't get as viscous during winter months when things get cold. And during summer since temperatures are higher, a lower grade gas might be OK.

This has been an ongoing discussion as to what gas one should put in an Rx400h, and the general conclusion seems to be that using a low grade gas is "OK" but doesn't yield the same performance (in MPG's and acceleration power) as a higher grade. There doesn't seem to be any evidence that using low grade gas will hurt the engine or anything, but since the Rx400h is relatively new, the symptoms might not have had time to show up yet. So who knows! I do know that using low grade gas can cause premature failure of various sensors in the engine, but I'm sure replacing a sensor after 10 years will still be cheaper than paying the premium for 91 gas each time at the pump.

[RX400h]

You can get away with lower octane gas when the weather is colder and intake air is more dense. Combustion cannot happen without both fuel and air with air making up a much higher percentage of volume.

[lemon]

It has nothing to do with the thckness of the gas - it has to do with resistance to detonation (octane rating). In fact as RX400h posted, you can get away with a lower octane when it's cold out, but when it's hot, THAT's when you should be running higher octane.

[cduluk]

Dammit! Good thing I've been using 93 year round... don't listen to me!