Do cars have a memory for fuel types?

feenster99 · 27 Apr 2006 at 19:00

Hi,
Odd question probably - I bought a 2002 Mini Cooper about 2 months ago. It was doing roughly 100 miles to £10 of fuel (fuel at roughly 90p/litre). I put £20 (@ 94.9p/litre) in the other day, and it has gone after 120 miles. I did stick some Optimax in and some Tesco 99 super magical stuff, just out of interest a couple of weeks back. It made the car run smoother it seemed, but now back on the normal stuff, it is running pretty lumpy (struggling to keep the revs up, and "gasping" when I put my foot down.

Is it likely that my car has adjusted itself to the richer fuel, and is there any way to reset this? (disconnect battery for 30 minutes is something I heard elsewhere)

Cheers,
Matt

MNuTz · 27 Apr 2006 at 19:03

couldnt tell you about the memory but i doubt it, however, is anyone else getting through fuel like no bodies business.

A tank used to last me and the g/f about 10 days, its lasting about 5-6 at the momet. a lot of people i know have made the same comment, seems as though the cars are extremely thirsty!

DannyDan · 27 Apr 2006 at 19:17

Maybe with it being warmer you use Air Conditioning more which affects fuel economy?

Skiddley · 27 Apr 2006 at 19:41

The engine management system will adjust to the fuel yes, it varies but typically a car is fully-adjusted after ~3 tank fulls. This applies to newer cars only (obviously).

Freefaller · 27 Apr 2006 at 19:47

It takes a few tank fulls for the ECU to adjust properly I believe.

feenster99 · 27 Apr 2006 at 19:55

Hi folks,
Well, I don't use the air con/climate control at all as I am tight

However, the resetting the ECU sounds along the lines I was thinking. Is there any way I can force it though? I thought disconnecting the battery did this?

Cheers,
Matt

Tdh1987 · 27 Apr 2006 at 19:58

The only thing i can think of a decrease in fuel economy is because of the hot weather. Less air molecules, so less power = more throttle.

Just a thought.

Freefaller · 27 Apr 2006 at 19:58

feenster99 said:
Hi folks,
Well, I don't use the air con/climate control at all as I am tight

However, the resetting the ECU sounds along the lines I was thinking. Is there any way I can force it though? I thought disconnecting the battery did this?

Cheers,
Matt

It depends on the car, my mondeo when I had it, you had to disconnect it for a few hours. And then you need to go for a varied drive, accelerating, braking, high speed etc... for it to get the best out of it. I then just went for an ECU remap and it sorted out all sorts of things and made it a bit pokier!

Skiddley · 27 Apr 2006 at 20:29

Tdh1987 said:
The only thing i can think of a decrease in fuel economy is because of the hot weather. Less air molecules, so less power = more throttle.

Just a thought.

would have thought the ECU would be monitoring air temp (density) and adjusting fuel quantity injected accordingly, I.e., hotter weather - less fuel to maintain the correct mix.

feenster99 · 27 Apr 2006 at 20:30

Having a nose around mini2.com, it seems the ECU is adaptive, and "updates" every few hundred miles (figures seem to vary from this to 1000 miles). There is a fairly easy procedure to reset it, so i'll do that first thing and see how it goes on my way to work.

I'll report back

Matt