That old cherry - the unleaded debate.

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p6steve

New Member
Hi guys - now I know there have been numerous discussions on this as well as very informative articles (John's in particular) in the magazine, so bear with me for starting another one, but to be honest I've found the information a bit confusuing and the amount quite overwhelming ???
I don't suppose there is a definitive answer to my question, but it really is as simple as what's best for me now unleaded is going !!!
Basically I have a series II V8 automatic and at the moment I use LRP with no problems (visible) whatsoever. I drive a reasonably gentle mixed 2-3000 miles a year on a very well maintained 65000 mile engine. I did put a few gallons of normal unleaded in a while back and it really didn't like it at all. I didn't have the timing adjusted as I was interested to see how much of an effect it had, but the car struggled to pull away at all and I had to douse it with good old LRP (in fact it ran better when I accidentally put diesel in a while back - but we won't go there again).
I don't want to spend a fortune (well I don't want to spend anything if truth be known), so what's the best thing to try first and what do I need to tell my mechanic with regards to the timing when I've changed liquids?
Here's hoping for lots more confusing replies and differing opinions!!

;)

Steve.
 
Steve,
You just knew that I'd reply didn't you?
As LRP is nothing more than super unleaded with an (unknown percentage) of additive then the easiest choice for you has to be super unleaded plus an additive administered by your good self. I can recommend Castrol Valvemaster Plus as my Three Thousand Five seems fairly happy using it with timing reduced to t.d.c. You may not have to alter the timing on yours if you have the engine which was originally buit for four star.
It really depends on what fuels are available close to your house - Super unleaded, Shell Optimax or Leaded?
If you have Shell Optimax near you then use that plus additive.
Hope this clears the confusion. Regards, John.
 
Steve - I can back up John's view. I have a '73 3500s and a '70 P5B. Since leaded was largely banned I have been using Castrol Valve Master with Octane Boost mixed with normal 95 octane unleaded. Both cars are as happy as larry. A bottle of this stuff costs around £10 and treats a load of petrol. It can be found in Halfords etc. I thouroughly recommend it as I have covered at least 10,000 miles (including lots of motorway) in the P6 with no hint of a problem. I think the fact the V8 is such a low revving lump probably helps!
 
Cheers John - you seem to be permanently connected to the forum so I kind of guessed you'd be one of the first!
Your reply has simplified everything so I'll give it a try in the next few weeks and let you know how I get on.
Thanks again,
Steve.
 
Hi,

I ran my 1974 P6B Auto for nearly 4 years on LRP (car has just been sold) and it ran fine with a standard ignition setting. 9.5 cpmpression engine fitted. When I fitted SD1 cylinder heads (since discovered that this was not necessary) and tried un-leaded the car hated it, with the ignition retarded to TDC, the car still hated it and ran hot. Put it back to normal and reverted back to LRP (Total - nearly always used the same supplier). Car was used every day as my sole driver and did around 6,000 miles per year.

My other car, a 1971 P6B Auto, which I have recently re-commissioned, having the 10.5 compression engine, was worried about using un-leaded, particularly as LRP was/is scheduled for withdrawal. Then I heard about Shell Optimax and have used this. I can report that the performance is very good and the engine will pink under heavy acceleration (rarely undertaken), engine only has 21,000 miles on the clock and is seemingly in good condition. I have used Millers VSP (?) fuel octane boost/lead additive and I did not notice any difference.

Therefore, Optimax would seem to be a good fuel to use particularly as it would seem (see previous threads on this Forum) that the V8 engines of post-1970 vintage can run on un-leaded fuels without modication and presumably LPG as well!

Good luck

Gary :)
 
Cheers for that Gary. I will be trying the shell optimax just as soon as I get down to Exeter where I keep my P6 and I've used all 8 gallons of LRP I've got in the tank at the moment...so about 80 miles :(
I'll let you all know how I get on..

Steve.
 
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