🤠 Scotty! My buddy's 2021 Civic's manual states that if the car is equipped with 18" or 20" wheels it requires '91 octane or higher... but if it has smaller wheels, then '87 octane is just fine... what gives?!? 🤔
What page of your buddy's owner's manual says this about octane?
The different sizes effectively changes the gear ratio necessitating the different octane.
What’s Andy doing on the forum?
who's Andy?
{black}:idontknow:
I just liked the face he's making
By way of explanation; If you put larger tires on the vehicle, you effectively change the final drive ratio higher (lower numerically) putting more load on the engine at a given speed thereby necessitating higher octane. If you put smaller tires on the car, you effectively change the final drive ratio lower (higher number) and need less octane to achieve the same result, there being less load on the engine.
are the tires larger?
No. It doesn't say that.
That was my first thought as well.
What does his owner’s manual say about refuelling?
Thanks for this, ITWT. I didn't want to go through the entire 635 page owner's manual.
Wha..
C'mon ITWT, gimme a break here! {black}:formalsmile:
It was aimed at the question, not your reply!
Woops! Lo Siento
Page 354
Rip my spine with 20” rims on a Civic..
Porkchop Sandwiches - re-read my answer on 9/27/21.
Thanks for photo. I was looking at the sedan manual which doesn't show this, but your friend must have the hatchback. (which needs a whole separate manual, apparently.)
Anyway, I think @doc is wrong. It has nothing to do with rim size because the outer diameter of the wheel will be the same.
Different trims come with different engines, and I think models with the bigger rims also have higher compression engines which require higher octane gas.
My next question would be which engine does it have? And which engine do the ones without the bigger wheels have?
I have been wrong before!
@doc you're never run bigger tires? Trucks and offroaders do it all the time. No change in gasoline required.
I run oversized tires on my lawn mower. The point is, oversized tires on a weanie little Civic engine loads it more, requiring higher octane. Big trucks and offroad rigs usually have much larger engines and sometimes a manual trans to compensate for the extra load.
since when does more load require higher octane? I can hook up a 9,000lb trailer to my truck and get no pinging.
octane has absolutely nothing to do with energy or power
Here are some numbers...
turbocharged engines often require higher octane gasoline. They are "charged" with more air, in other words, the cylinder is compressing more air - high compression.
Hence my earlier question regarding engine type. Maybe the 2.0L Civic is fitted with the smaller wheels?
Wait, might trim levels be a factor? My husband’s 2021 Civic EX (4-door, hatchback, 1.5L turbo, CVT) calls for 87 octane... and it has 17 inch wheels!
It could be... with all the different trim level combinations, who knows? Scotty, help us figure this one out! {black}:idontknow: