Octane Rating

[vanquish spirit]

I am just timing up my 1971 Range Rover post restoration and need to set the advance. If I run it on unleaded with a fuel additive can anyone tell me what this octane equates to in old money. In other words in RON as we know it today comparable with octane ratings from the early 70's? I think 2 star was 85 and 4 star was 88? I fear unleaded is 95? in which case it will be way off. Damm progress!

[tvrgaas]

I thought 5 star was 100 octane (RON) and 4 star about 98.

Many of the adatives will increase the anti knock and hence Octane rating.

[AJAX50]

RON is a standard measure. The RON of 2* was 92 I think, 4* which was leaded was 97 or 98. Unleaded is 95, an additive will give you about two points but this does depend on the constituents in the blend, so could be less benefit.

vanquish spirit said:

I am just timing up my 1971 Range Rover post restoration and need to set the advance. If I run it on unleaded with a fuel additive can anyone tell me what this octane equates to in old money. In other words in RON as we know it today comparable with octane ratings from the early 70's? I think 2 star was 85 and 4 star was 88? I fear unleaded is 95? in which case it will be way off. Damm progress!

[Matthew-TMM]

5 star was 100 RON
4 star was 97 RON
3 star was 94 RON
2 star was 91 RON

They may have varied a little over the years, but those are the figures I've seen.

[SB - Nigel]

Matthew-TMM said:

5 star was 100 RON
4 star was 97 RON
3 star was 94 RON
2 star was 91 RON

They may have varied a little over the years, but those are the figures I've seen.

I agree, I'd say (IIRC)

5* 99-100
4* 97-98
3* 94-95
2* 91-92

BUT I'd suggest you check with the Landie forums as I thought the RRV8s were lower compression and would run on lower octane fuel (??? I may be wrong)

PLUS some tests have show octane booster do not boost octane

I've used Tesco 99 for my 4* and 5* drinking classics and recommend it (if you need it)

[vanquish spirit]

thanks a lot guys. Let me check the original book. Mine was a 8.5: 1 compression ration, which is the lowest they made. I guess that means it is running at TDC on 2 star and 3 degrees before on 4 star. So if I put unleaded in plus and additive I can get work it our from the above. I hope! thx

[SB - Nigel]

I'd still check with the Landie lot they'll know also check with them if you need an additive ( lead replacement and/or octane boost)

Remember check twice, do once

[niva441]

The Rover V8 doesn't need lead for the valves, only the octane rating. But as yours is an early Range Rover, it shouldn't need the octane (assuming standard). My factory MGB V8 ran fine on standard unleaded.

[vanquish spirit]

Good advice guys thanks a lot. Actually on an anaorak point my Rangie is an 8.50 :1 small valave head and was made for only a few years in the Rangie. RPI suggested to me that the valve inserts in my heads were not hardened to the extent of the later type, or in other words it needed later heads or hardened seats fitting. I havent as yet and with the additive and timed now to old 4 star spec it seems to be running about 98% correctly. The 2% feels a bit like dizzy wear which I am going to check on a friends Crypton. cheers

[AJAX50]

If you do use additives, stick to one type, they are not compatible; one purges anothe off the valve seats. I used the manganese based Castrol octane and valve seat additive for 20,000 hard miles in my Healey before I needed to do the exhaust valve seats.

vanquish spirit said:

Good advice guys thanks a lot. Actually on an anaorak point my Rangie is an 8.50 :1 small valave head and was made for only a few years in the Rangie. RPI suggested to me that the valve inserts in my heads were not hardened to the extent of the later type, or in other words it needed later heads or hardened seats fitting. I havent as yet and with the additive and timed now to old 4 star spec it seems to be running about 98% correctly. The 2% feels a bit like dizzy wear which I am going to check on a friends Crypton. cheers

[Balmoral Green]

As far as additives go, tetraboost comes highly recommended, as it isn't really an additive like the others, it is real lead, and it's an octane booster too, so you can make as much real leaded 2,3,4 or 5 star as you want.

http://www.tetraboost.com/

[RichB]

Indeed, Tetraboost is the best, it's also expensive and highly toxic It's basically tetra-ethyl lead and you need rubber gloves to handle it. When added to unleaded petrol it makes leaded fuel, indeed it's exactly what is used to make Bayford Thrust 4* so it's really is the real-deal. I researched this a few months ago intending to use it in my Aston, instead I discovered that the previous owner had been remiss in using lead additive and the valves had receded too far into the head so a full unleaded head conversion was the best way to go. With Tetraboost fuel works out to about £1.70 a litre vs' £1.45 for Bayford Thrust so I can tell myself that every time I fill up with ordinary unleaded I'm recovering some of the cost of the re-built head!

[niva441]

Practical Classics ran a feature on additives a few months ago, I'll see if I can find a copy.