High or low octane unleaded ? R4 GTL

[Suffolk789]

Dear All,

What is the consensus on high octane or low octane unleaded fuel in an R4GTL engine ?

 

[malcolm]

There isn't a consensus.

Modern fuels just don't seem to be as good as old ones and the Renault 4 tends to run lean anyway. If everything is in good condition it shouldn't make a lot of difference whether you use 95 or 98, or if you are running a bit lean it is possible to enlarge the main jet a little from 0.8mm to 0.9mm and run happily on the lower octane fuel. You can tell if that will help by pulling the choke out a tiny bit to see if it runs better.

I've found the modern fuels to be a pain in the Gordini which has a much higher compression ratio. I use 98 octane in that, and still haven't got the carburettor jetting quite right. I had to enrich the secondary jet of the R5 TX which was having trouble on full throttle and now that works well on 95.

 

[reidalpine]

Hi Malcolm -and Suffolk..What is the situation in the uk these days re ethanol-mix in petrol? Do you still have un-corrupted petrol in any
of the RON/Octane settings? 95/98 etc? as you say; the motors seems to be running leaner than before,so i think it would be a good idea for
you to show just How to -and Which jet to enlarge or change on here.. (I hate to imagine you're idle over there Malcolm
-In both France and Germany I think you'll have to tank up in smaller villages as they seem to Only sell corrupted (Ethanol-mixed) petrol along
the motorways/Autoroute/Autobahn...
Here in Norwayland a few of the stations still offers the real thing,but it seems we are forced to follow suit as set by the Geeks in Brussels..-R.

 

[malcolm]

I think we mostly have 5% ethanol at the moment. The jet I changed on the TX was the air jet in the secondary choke as I had a smaller one from a Gordini carburettor. Has much the same effect as making the main jet bigger in the secondary. I can't remember which jet that is physically.

 

[reidalpine]

same here,5% but it's also known that stations has gone well over the 5% as this is more cash-in-pocket for them.... Strange thing here is
they do not mark the pumps accordingly (say 5% ethanol) so in effect, you do not know what you put in your tank.They cal it all sorts of fancy-names like More Miles etc
Reality is you use approx 30% more fuel on E85 so there is no gain at all -Reid.

 

[jjad]

No problems in our GTL running regular 95 octane petrol.

 

[Suffolk789]

Thanks everyone for your comments !! I will probably stick with bog standard unleaded. Does anyone ever use additives ?

 

[jjad]

Yes, Castrol Valvemaster (not Valvemaster Plus).

See this thread: http://renault4.co.uk/forum/threads/firing-on-three-cylinders.6501/#post-42285

 

[David M]

I'm running a Renault 5 GTL.*

I use 98 RON so that I can get the maximum performance from the car.
Isn't that the joy of ownership?
Downunder, the higher octane fuels have more additives to clean the engine (according to the advertisements) BP and Shell operate here as I guess they do in the UK.
So, I figure for the additional cost, I am maximising engine power and longevity before my next rebuild. No doubt the next iteration of the motor will inevitably increase horsepower and the need for better fuel. (higher lift cam, 2bbl Weber downdraft carb)

*So it's a 1289cc unit with the same gearbox (31:10) final drive. At the end of the day, I'm probably paying more money for fuel to buy a little more psychological satisfaction. With an old and rare car, I think that it is a reasonable decision even if the fuel company gets as much comfort as I do.




David