Will running a 98 RON car on standard unleaded cause any problems?

[anonymous-user]

My friend has a 2006 Boxster S that he bought when it was 12 months old, and we ended up next to each other in the petrol station on Sunday and I was filling my 993 up with Shell V Power or whatever it's called and I noticed he was filling up with standard unleaded.

I asked him if it wasn't supposed to be run on super unleaded, to which he replied "dunno, but this is cheaper". So I had a look on the inside of his fuel cap and it has the same sticker as mine which says 'Super Unleaded only - Minimum 98 Ron'.

He says he's not going to be buying super unleaded anytime soon because of the price of it, and he also says it's made no difference to his car.

Perhaps I'm the one getting mugged by super unleaded??

What difference (apart from a very minor reduction in performance) will using 95 RON petrol make to a car over a long period? Could any damage occur?

Thanks

[kambites]

Assuming the Boxster has a knock sensor (which I think it does?), it'll just retard the timing a bit to compensate so it shouldn't cause any issues beyond slightly less power and slightly worse fuel economy.

The drop in economy might be enough to more than counter the difference in fuel price though, it varies from car to car.

[HellDiver]

Are you likely to be paying for any repairs needed on his car?

[adycav]

Hi Tim - I can't speak for the Boxster, but I tried running my 993 on regular unleaded for a couple of tanks and I definitely noticed the difference (I usually use V-Power).

The car felt more hesitant at low/mid rpm and breathless at the top end. It also seemed less happy at idle when warm (traffic lights etc) - sounding like it was 'hunting' slightly.

I also noticed quite a difference in mpg - not got a trip computer in mine but I was getting 5-10% less miles out of a tank.

As your 993 is such a magnificent specimen (with £££ spent on it) I would not be tempted to downgrade the fuel.

[john_p]

If it's designed to run on 98, then running 95 will result in reduced power output. It could damage the engine if it hasn't got the hardware to "detune" down to the lower octane level. (Knock sensors etc). So basically, why drive a Boxster if you can't afford to run it

It's not so clear cut in the other direction. I don't think most cars get any appreciable benefit running 98 when they are set up for 95, despite what Shell's marketing department tell you..

[anonymous-user]

HellDiver said:

Are you likely to be paying for any repairs needed on his car?

Of course not, but being a good friend I would like to advise him on the consequences of lower RON fuel, if there are any.

He is not 'mechanically minded' as to consider the effects of different fuels.

If there may be some problems caused, and I advised him as such, then he would probably consider a change to Super to avoid the issues.