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they're the same "98 octane" so is it ok to mix petrols?

or just stick to the onoe bp ultimate? :devil:

there is really no difference between BP98, mobil 98, caltex 98, shell 98. the only differences you get is between servos and batches. sometimes any company will have a bad batch, or some contamination, or you are unlucky enough to buy from a servo with low stock (ie getting fuel from the bottom of the tank) or with old stock. but apart from that it doesn't matter one bit really which 98 brand fuel you buy.

spent a week cruising the hinterland behind coffs harbour last year while the old girl did some business there. I had the luxury of a BP, Shell, and a caltex within 5 minutes of where i was staying so i tried them all. The caltex returned the lowest knock reading of them all. Only talking a couple of points and, as has already been pointed out it could just be different batches causing the slight variance But i wouldnt worry about using any of those 3 in a car tuned to 98 fuel.

Edited by FineLine

well unless i got a bad batch i will have to disagree with everyone

My car was tuned with bp ultimate 98, i never got above 12 no matter what i did

I put in some Caltex vortex 98 and my knock values went through the roof at high rpm. I went to 6900rpm and knock when from 6 to 66 in an instant.

Tune was spot on too

i dunno what it is guys...but in my stock r32 gtst before the half line i can get 230kms with bp ultimate...as soon as i change to something like v power i can get about just over 200-210kms at half way?

but yeh don't think there are probs with mixing petrols...the focus, corolla, swift daily drivers in most cases would probably switch from 4 different brand fuels because they would most likely get whatever is close to them at the time of needing fuel.

I use BP98, Mobil 98 and united 98. Find no difference between either of them. Unless your sitting on the freeway doing the exact speed and accelerating up to speed the same you cannot tell the difference. You might floor it harder for longer 3 times more in 1 whole tank of driving.....you might drive for an hour longer in slightly warmer weather which should make it run slightly richer (depending on ecu).

In terms of knock the turn over the servo has plays a big part in the age of the fuel. Try to fill up at servos that a fairly busy.

  • 2 years later...

@llusions lol I've done the same thing. I realised after putting about 20L in, so just stopped and picked up the 98 and waited for the staff to unlock. You'll be fine running even 91 as long as it is in low ratio, ie 10L out of 60L tank, with the rest being 98 but not recommended. A friend in the country says he carries around a bottle of octane booster, for if he's ever stuck with only 91/95 at a station. Obviously you don't want to do it for long, but as long as the knock is minimal you'll be fine.

Brand wise, they all use the same refineries so really doesn't matter.

98 RON fuel is 98 RON fuel regardless, it is refined to the same standards, so there should be no difference in mixing between brands.

It is generally only bad batches that cause inconsistencies in quality, or if your unfortunate enough to go to a station that has its tanks quite low then you may find minor issues in fuel consumption and power to an extent, but usually not to the extent that it can be noticed from a drivers point of view - maybe only a hand controller or similar showing slightly higher/lower knock readings.

Massive (unsafe) differences in knock levels can only be down to using a lower rated fuel ie: 95/93/91, or an EXTREMELY bad batch of 98, which would be rare.

Further to knock levels and such, as a car gets older especially if it gets out of tune, you might need to increase the octane of the fuel. For example 93 to 95, or 95 to 98. Not so applicable to Skylines, but other 'sports' cars have this problem. Anyway, a good $200 tune should fix that, but just bear in mind you can't always use the fuel in the manual/theory, as reality is different.

personally I have had my car tuned on vpower with a result of 267rwkw and then 278rwkw on the same dyno (different day, however the higher power figure was on a MUCH hotter day)

I only run my cars on ultimate or (manildra e85), and was driving my mates 34 the other day and needed to fill up, the only BP around was closed so I was forced to go to shell. as soon as I left the station the engine check light was flashing under high load.

I have also heard that vpower is a 95 octane fuel with an octane booster to acheive 98ron whereas ultimate is refined as a 98ron

also i know of a few tuners that net lower power figures on shell "fuel" when compared to ultimate.

i dont't have any concrete evidence to back up ANY of these claims, but take it how you want ;)

i do NOT use shell

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