What fuel should I use?

[lee]

Hello
Can someone please tell me if I  can use super unleaded 97,  because everyone else says I should use 98 but cannot get this where I live,  unless shell optimax is 98.

Any help would be much appreciated.

[kevin]

super ul is fine and  yes optimax is 98/99 ron
regards kevin

[richandhazel]

Shell Optimax (98/99 RON) is the ideal fuel to use, super unleaded (97 RON) should be fine. All the GTI's can run as low as unleaded (95 RON), some just require ignition timing retardation, others the knock sensors sort it out via the ECU. What car have you got?

[lee]

Cheers mate

I have a 1989 16V GTI small bumper bog standard.

[richandhazel]

Ignore the following, it applies to American spec, not European/UK spec

Just had a look in my workshop manual and I think you have the TCI-h ignition system with knock control, although I may be wrong. Easy way to check is to have a look at your distributer. Are there any vacuum lines going to it. If not, as I suspect, then the ignition timing is electonically controlled via knock sensors. That being the case, you can use unleaded (95 RON) too. Have a look here for a little more info:-

http://homepage.ntlworld.com/richandhazel1/Knock/Knock.htm

[lee]

Thanks alot Rich

I don't have any vacuum pipes on the distributor, so I'm gonna use Optimax.

Thanks for your time and information.

Lee

[A9WYN]

knock sensors, e.c.u. on an '89 gti16v i had a '91 jetta 16v K jetronic f.i. no ecu no knock sensors had to use leaded or super unleaded because . no engine management control, only fitted on 8v digifant engines

[richandhazel]

knock sensors, e.c.u. on an '89 gti16v i had a '91 jetta 16v K jetronic f.i. no ecu no knock sensors had to use leaded or super unleaded because . no engine management control, only fitted on 8v digifant engines

I agree all 16V's have the CIS-E fuel injection (K-jetronic). However, I'm looking at the ignition system (as its the ignition timing that has to change according to what grade fuel you use) and based on the information in my Bentley (admittedly American biased, but I think the principals remain the same, just different engine codes and terminology) there is an element of knock control incorprated into the ignition system. Its a lot more basic than the difigant. Unfortunately I haven't got a 16V to look at, which would help but if you have a look here you can see where I'm coming from:-

http://homepage.ntlworld.com/richandhazel1/Ignition/system.htm

[A9WYN]

american 16v engines were different from uk/europe spec. 16v's they all had catalitic converters fitted plus lambda probe /ecu control and could run on premium unleaded petrol unlike uk spec. cars

[richandhazel]

Oh OK, yeah I must admit I have come across these differences with the Audi's. I'll have a look in the Haynes manual and see what that says. I must admit I do tend to use the Bentley all the time as its just so much better than Haynes.