Petrol debate on older cars

Post by **SoLaMaNdA** » 03 Mar 2006 09:45 am

I've had many people say that the older 2l volvo engines need LRP or high octane (like my 1984 360). I usually run plain unleaded and noticed something interesting when changing spark plugs last weekend. They are an exact image of the 'normal' plug as seen on the champion guides in the back of haynes manuals. Maybe unleaded is fine after all!

Post by **dalahare** » 03 Mar 2006 01:51 pm

Still could be doing unseen damage, as leaded fuel helped prevent valve seat recession, it will be intresting to see what others have to say.

Post by **Fuse** » 03 Mar 2006 02:40 pm

Volvo engines with aluminium heads don't nead leaded fuel. High octane is reccomended though with higher compression engines.

Post by **foggyjames** » 03 Mar 2006 09:28 pm

Fuse is bang-on. They have hardened valve seats, so no lead needed. Octane is the problem, but if it's not pinging, don't worry about it.

cheers

James

Post by **SoLaMaNdA** » 03 Mar 2006 09:37 pm

Yeah, always thought the same James. No pinking and decent plug condition is a good sign to me, unleaded is ok (for when someone else asks).

Post by **Ronnie** » 04 Mar 2006 01:53 am

I know that my '85 360 runs much better on high octane fuel. I use 97 RON petrol with LRP additive with octane boost just to be on the safe side.

Post by **classicswede** » 04 Mar 2006 12:50 pm

The only volvo ohc engines that need the higher octane is some of the turbo motors. There are no problems with valve seat recession or guide wear. The older B18 and B20 ohv engines do not suffer seat recession but the do have problems with valve quide wear - this can be solved by changing the quides. The only adjustment needed for running volvo engines that were intended to run on 4 star is to adjust the timing by ear rather than the book.

Post by **foggyjames** » 05 Mar 2006 12:16 am

Early 10:1 compression B200s are rated for 97 octane in the manual, same as a 740 TI. Whether you need it or whether it's just there as a safety margin, I'm not sure.

cheers

James

Post by **Ronnie** » 07 Mar 2006 07:51 pm

I've had this conversation before with dubheads. Basically the consensus was that if a car is designed to run high octane fuel (ie 4 star) then you'll get better mile/£ with high octane fuel unless you adjust the timing to compensate.

Basically my car feels noticable more lively with high octane fuel right across the the rev range. It responds quicker and is more free revving. I've had Volvo themselves recommend I use LRP, and an independant mechanic who I rate advised me to use LRP in every other tank full. I use it every time just to be on the safe side.

Post by **foggyjames** » 07 Mar 2006 08:39 pm

Question is...do you have to run LRP, or would 'super' unleaded (ie: not 95 octane) be just as good? I'm placing my bet in the latter camp, as the only fundamental difference is the additive content.

cheers

James

Post by **Chris_C** » 07 Mar 2006 09:05 pm

I know Andy always runs super. If it is just the octane for the compression ratio, why wouldn't super be as good? Could always get some jap fuel in

Post by **foggyjames** » 07 Mar 2006 09:10 pm

My thoughts exactly Chris.

cheers

James

Post by **ebdl** » 08 Mar 2006 09:36 am

If you really want to treat your car nicely and get the best performance out of it, I think Shell Optimax is the only petrol that's been proven to actually make a difference (I think it was Top Gear that tested various fuels out).

In my experience in the 850, even Shell's regular unleaded is noticeably better than the supermarket stuff. My fuel consumption is definitely better on Optimax (by about 1.0 - 1.5 mpg, so I'm not sure it's cost effective) and performance seems perkier, although that's purely subjective. I've not found any benefits from other brands, although Texaco stations are rife in the South West and seem better than supermarket fuel.

Post by **foggyjames** » 08 Mar 2006 08:20 pm

ebdl wrote:In my experience in the 850, even Shell's regular unleaded is noticeably better than the supermarket stuff.

I'd go with that. I buy Shell fuel whenever I can.

cheers

James

Post by **classicswede** » 08 Mar 2006 09:00 pm

I cant be bothered using 97ron 117ron is so much better - no chance of pinking