Im wondering what type of petrol most of you use for your L series motors.

I know they mostly adapt to unleaded quite well, but ive been told that its quite a dry fuel, and can lead to valve seat recession. Im currently using unleaded in my l24 and ive not had any problems, however, a friend mentioned to me that there are various lead or zinc based additives that can prevent vsr. How often would you add a product like this and is it necessary?

Also, despite these engines not being designed for unleaded, is 98 octane beneficial, due to it burning cleaner? Any help would be much appreciated.

Tom

I use LRP since the engine was made for leaded fuel... I've used unleaded a few times with the additives but didn't really notice much difference except it was annoying to do and not cheap either.

I think you can get something done to your engine (hardened valve seats?) which will let you use unleaded. Perhaps someone can clarify...

Depends what your valve seats are made of, If they're brass, the need a lead replacement additive. If they're steel or bronze (My E88 head has bronze)then you'll be fine using normal unleaded.

I've also heard that the LRP you get is really, really ordinary fuel. Leaves visible deposits in intakes etc.

As for optimax, I think it does go longer on a tank, but I don't feel any difference in performance -(don't have any crazy mods though).

Luke

Yeah the prob is that its 'lead replacement' fuel, and ive been told, like you said luke, that the quality of that fuel is abysmal. Ill have to check what head i have, is there any way of knowing without ripping the thing off? Given that its a 73' 240k though, the chances are that its an earlier brass valve seated head...Does anyone know of any particular brands of additive? I think i have heard of valve seat hardening too, lachlan, but im not sure where you could get it done and how exp. it is...

It should say on the head itself between plugs 1 and 2, or around that area, what head type you have, my bet is E30. Regardless of which you have though, being the car is over 30years old, unless you open her up to check you'll never really know for sure, I use an additive when I remember to do it.

Cheers michael, thanks for the info. Out of interest, what brand of additive do you use?

Tom

Valvemaster, comes in either wee orange squirty tubes or you can buy bigger bottles, keep in mind though, I am in NZ so.. perhaps you don't get that brand there?? I have no idea.

Oh, and I think the ratio is something like 10ml to every 10l ?? So when you buy a big bottle, it will last a while.

Ill have to find out, thanks heaps.

I know this topic is damn old, but i only just landed back in the country soooo....I checked my head and its an E60. Anyone got an idea of what the valve seats are made of on that?

Just a word of warning about "Optimax", my local motorcycle mechanic has had to rebuild several motorcycle carbs due to Optimax causing the seals to dry up (I am sure there is a technical term for this), this is also applicable to carb equipped cars.

Shell has designed the fuel for use in E.F.I. engines and my experience is that it should probably be left there. My understanding is that the P.U.L.P made by Mobil does not have these prob's (although I can't remember what it is called)

I have been using Mobil P.U.L.P. with valvemaster and have not had any prob's, but I don't drive my Z everyday.

Rusty