austin_d_powers

I was watching a program about the history of oil the other day, and they explained what the octane scale was all about.
Like most people I was under the impression that higher octane fuel was better quality. Turns out its another one of those scams, like changing the oil every 3000 miles. The higher the octane, the more the fuel can be compressed without spontaneous combustion occurring. But all cars can use any octane fuel for normal driving conditions. High octane fuel is only useful in extreme high compression conditions, such as racing. Even if your car was capable of reaching conditions that might make high octane fuel useful, just how much racing can you do on public roads?

Dan725

With some cars its recommended (by the manufacturer) that you use the higher octane stuff, its often the case with superchargers and turbochargers, and highly tuned motors. As you have rightly said, its to prevent detonation, but the requirement is not as high as you might think, ie not just for racing etc - the cars are set up to require the higher end fuel if thats what they say to use. Basically, whatever is recommended - use, especially if your car is under warranty...

BritGuyTN

less labourious detail

petrol is measued in two ways for octance RON - and MON

UK - they just use the RON rating for what you see on the pump

USA - the add the RON and MON then divide by two for what you see on the pump

As MON is a smaller figure than RON the overall USA octane level is smaller

I would be interested in knowing the RON only rating of the petrol at by local BP in Nashville

if when you open the petrol cap it asks for a certain octane then I would suggest using that one.

as generally cars that require the higher octane tend to be priceier, you should be able to afford the extra buck or two when you fill up

austin_d_powers

Yes, but even these cars don't really need high octane fuel unless driven in a manner that causes the engine to run extra hot inside the piston chamber.
Small engine, high power output, high revs, high heat (race car).

Dan725

Ah, but theres still not much point putting lower than recommended fuel in there just incase. Besides, if you buy a car thats fast, you want to at least know you can give it some stick without worrying about it

TRPardoe

It all comes down to knocking, or "pinking" as we used to call it.

No matter how you drive your gasoline engined car, if the engine doesn't knock under load then it is happy with the fuel you are using and there is no need to waste money on a higher octane version.

Scorchio

I never changed my oil in the UK, other than when the car (Peugeot 106) was due for it's annual service. This was doing approx 11k miles per year.

My new Honda Civic manual states I should change the oil every 10k miles - however the guy at the dealership recommended 5k instead. He's got to feed his kids, you see.

BritGuyTN

yeah - along the same lines that in the UK i needed 1 filling from the dentist, over here I needed 8

the thing is, the muppets at the oil change place sound so convincing when they say they would not let it go more than 3000 with out changing

the way i look at it - if they knew more than the engineers at the manufacturers then they wouldn't be working where they do

to be honest, the only people I think have a valid opinion how often a cars oil needs changing are the engineers who design and test the things - i think most other people are blowing smoke out of their ass

ScyLarc

I'm ashamed to admit that i don't have a clue how to go about changing my cars oil. Do they usually put instructions in the manuals?

Bob

Jiffy lube, lube express...whatever, it's quicker and easier, don't have to worry about dumping the old oil...

Bob

Aye, well the honda civic R-type, even when ragged hard can do 15K miles without an oil change, even though the manual says 10K...I know that, because my mothers mates with the chief engineer that designed it....they just like to cover there bases and make sure that the engines' don't blow on people...

TRPardoe

p.s. We have two Ford GTs in the showroom. One is red with white stripes and the other is white with blue stripes.

If anyone needs to buy premium fuel, they require 91 octane.

A cool $260,000 might reserve one of them for you.

Pimpbot

We do it every 3000 or there abouts. We mainly stick to this in case we ever have a problem and the dealer blames the lack of oil changes or some other type of shister excuse. It costs $24 dollars from our dealer.

rincewind

I just got a new motor and I don't have to touch it until 10,000 miles.

I wouldn't change my oil every 3,000 miles but that's me.

BritGuyTN

is that the mini?

good old bmw engineering