What fuel should actually be used? 99, 98 or 95

[Pig benis]

Hello guys

Recently I have gone out and treated myself to a Subaru Impreza WRX (2.0) and now I can see why people buy these things. They are an absolute hoot to drive and I am thoroughly enjoying mine.

However, I have been on the Subaru owner forums to clear up my confusion as to what fuel I should be using. Currently I am filling up with Tesco 99, but from reading lots of different forum posts, I am not entirely sure if this is the best stuff for my car. So I was hoping you guys could clear up any confusion?

I haven't filled the car up with regular pump fuel, but I take it this will make my engine run rough?

Thanks all
PB

[Pig benis]

Thanks for all the replies everyone.

So the car is a 04 Impreza WRX, it is absolutely mint, with only 40k miles. It isn't quite an STI that I was after, but this car came up and I just had to have him. So I'd like to keep it in the best condition that I can.

As mentioned above, I am using Tesco Ultimate, where I have noticed the car will stutter ever so slightly (occasionally) on full throttle. But the car doesn't do it on BP's finest. I initally thought it was just a bad batch of fuel from Tesco, but it has done it on 2 other tanks

I am thinking of getting my car mapped very soon, is it possible to have a switchable map? One map for daily driving on 95, and then another map for running on the good stuff?

Thanks all
Vince

Edited by Pig benis on Thursday 20th October 20:04

Edited by Pig benis on Thursday 20th October 20:05

[Pig benis]

Ahbefive said:

If you fill up your tank once a week and the difference in price between 95 and 99 is 6p per litre that equates to around £150 a year. Then you consider the economy saving may nearvenough negate that saving.

Why would you want to use 95?

You make a very valid point here, I totally agree. This is my first car that needs 99, but I wanted to make absolutely sure I was filling up with the correct octane.

All I need to do now is, replace the pea shooter style exhaust pipes on the back with something that is a bit more throaty. If anyone knows of any prodrive backboxes going, please let me know

[Pig benis]

Hello Subaru folks

I have now had my Impreza for 3 months and in the time it has used a LOT of fuel. Which has given me the opportunity to sample different fuels, and here are my findings -

Tesco momentum - the car runs smooth and feels like it should do, but the MPG is shocking
Tesco unleaded 95 - the car runs exactly the same as above, but I will get on average 40+ miles more per tank
BP Ultimate - No different to Momentum
Bp unleaded - Juddering on idle

The thing that surprised me the most is the Tesco unleaded. My car ran perfectly fine, and I got more MPG on every fill up. I did make sure that I put two tanks of this stuff into my car before I started noting the figures, as I still has 1/4 tank of Momentum. Why would my mpg have increased? It goes against all the advertising, and also the car felt perfect.

My Subaru is box standard, so maybe it is just the mapped cars that need to run the more expensive juice?