Question About 85 Octane Fuel (luxury, live in, safe)

[Left-handed]

I recently purchased a Lincoln MKZ and the recommended fuel is Regular Unleaded. Around the rest of the country, that's 87 octane, but as most of you know, it's 85 octane in most of Colorado. Anyone here drive a 'luxury-brand' car and use 85 octane fuel without any issues? Or is it better to play it safe and use 87 octane?

[SkyDog77]

I live in Arizona and use 87-octane regular. In Utah, Idaho and Nevada, stations were selling 85-octane as regular gas. This forced me to pay more for midgrade 87-octane. Is this the latest petroleum-industry scam to get more of our money? Will my car run okay on this bogus 85-octane regular?

A:
Octane is the ability of a fuel to resist knock, and high-compression engines tend to knock more. The obverse of that is that lower-compression engines can run on lower-octane gas. Air is thinner the higher above sea level you go. Less air going into the cylinders means less pressure at top dead center when things go bang. It's a lot like lowering the compression ratio in the engine, reducing the need for high octane. Cars will run just fine on lower-octane fuel when they're well above sea level--and all of those states are. Hopefully, by the time you get back down to denser air, you've burned off most of the low-octane stuff, and can refill the tank with higher-grade fuel.

30 Car Mysteries Solved: Low Octane Fuel at High Altitudes

[Left-handed]

Originally Posted by SkyDog77

30 Car Mysteries Solved: Low Octane Fuel at High Altitudes

Squeezed
Q:
I live in Arizona and use 87-octane regular. In Utah, Idaho and Nevada, stations were selling 85-octane as regular gas. This forced me to pay more for midgrade 87-octane. Is this the latest petroleum-industry scam to get more of our money? Will my car run okay on this bogus 85-octane regular?

A:
Octane is the ability of a fuel to resist knock, and high-compression engines tend to knock more. The obverse of that is that lower-compression engines can run on lower-octane gas. Air is thinner the higher above sea level you go. Less air going into the cylinders means less pressure at top dead center when things go bang. It's a lot like lowering the compression ratio in the engine, reducing the need for high octane. Cars will run just fine on lower-octane fuel when they're well above sea level--and all of those states are. Hopefully, by the time you get back down to denser air, you've burned off most of the low-octane stuff, and can refill the tank with higher-grade fuel.

Thank you!

[Quietude]

Also appreciate the link/answer. I was wondering but hadn't gotten around to asking about it...

[TigerLily24]

Originally Posted by Left-handed

I recently purchased a Lincoln MKZ and the recommended fuel is Regular Unleaded. Around the rest of the country, that's 87 octane, but as most of you know, it's 85 octane in most of Colorado. Anyone here drive a 'luxury-brand' car and use 85 octane fuel without any issues? Or is it better to play it safe and use 87 octane?

Much as I hate to pay the extra whatever for the 87 octane, that's what I've done since I've lived here.
I know people say it doesn't matter, but that hasn't been my experience.
I tried the 85 in my 4-cyl PT Cruiser once and it knocked like crazy.

I drive an 8-cyl now and only ever use the recommended 87 octane.
Yes, it pains me to spend more, but I live with it.

P.S. Congrats on your new car! Love that model.

[SkyDog77]

Originally Posted by TigerLily24

Much as I hate to pay the extra whatever for the 87 octane, that's what I've done since I've lived here.
I know people say it doesn't matter, but that hasn't been my experience.
I tried the 85 in my 4-cyl PT Cruiser once and it knocked like crazy.

I drive an 8-cyl now and only ever use the recommended 87 octane.
Yes, it pains me to spend more, but I live with it.

P.S. Congrats on your new car! Love that model.

The good news is you’ll know right away. I have an 8 cylinder Toyota that calls for 87. I run 85 with zero knocking issues.

[guyatwork37]

And I was sitting here like an idiot just paying for 87 octane because that's what was recommended in the manual for my 4 cylinder Subaru Legacy. Now I know. Thanks!

[wilberry]

I have a new Hyundai Veloster and it came with this ;" Your new vehicle is designed to use only unleaded fuel having a pump octane number ((R+M)/2) of 87 (Research Octane Number 91) or higher. " I use 85 reg unleaded and it works just fine.

[Quietude]

Originally Posted by guyatwork37

And I was sitting here like an idiot just paying for 87 octane because that's what was recommended in the manual for my 4 cylinder Subaru Legacy. Now I know. Thanks!

Only a few cars absolutely require anything higher than 87, 85 way up here. Most that recommend higher octane have adjustable timing and fuel control, so that you get slightly lower power and economy with regular but can use it just fine. I had a Volvo that absolutely required 91, no substitutions allowed. My Hondas have all been flexible.