Lotus Elan

Unleaded Or Leaded That Is The Question

PostPost by: androb » Fri Nov 12, 2004 6:19 pm

Just wanted to see if someone out there can tell me what is required to get my s4 webber headed elan to drink unleaded fuel have had conflicting info from replace all seats and bronze guides or replace exaust guides and seats are hard enough to cope "stainless steel valves? " etc just want honest advise .I am lucky that I have a local garage selling leaded petrol but for how much longer? looking for a long term fix do not want to be removing head because of exaust valve /guide problems later on many thanks for any help
Posts: 2
Joined: 12 Sep 2003

PostPost by: worzel » Fri Nov 12, 2004 7:42 pm


Try TetraBoost if you don't wish to lift the head.

This is Tetra Ethyl Lead (the real thing) so you can make 4 or 5 star if necessary.

If you don't do a lot of miles it makes sense.

Fourth Gear
Fourth Gear
Posts: 626
Joined: 13 Jan 2004

PostPost by: 1964 S1 » Sat Nov 13, 2004 12:38 am

I live in the midwest USA, buy brand name gas, Shell, BP, Marathon, etc. I've owned a restored S1 Elan for about 6 years, a Stromberg +2 for 5 years and just sold an S4 with Webers. The only time I've bought leaded gas is when I put racing fuel in them the few times I"ve drag raced at the local British Car Day. I've never had a problem concerning valves etc. I use premium unleaded fuel and can cautiously boast of more than 15,000 trouble free miles.
1964 S1
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1472
Joined: 15 Sep 2003
Location: Hamilton County, Ohio

PostPost by: brassringfarm » Sat Nov 13, 2004 10:49 pm

Dave - Check the archives for a more thorough discussion - but this topic has been discussed several times before. The valve seats are hard, as they are inserts into the alloy head - unlike some old US cars that had valve seats that were just cut into the cast head. I've been running premium unleaded and things are fine. Don't worry about it - regardless of local mechanic comments.
Paul Zimmerman
65 S2
Second Gear
Second Gear
Posts: 224
Joined: 08 Jan 2004
Location: Geneva, Switzerland

PostPost by: paros » Sun Nov 14, 2004 8:13 am

Hi, as a follow up to this question. I have had it suggested that there is a big difference between old leaded benzol petrol of Elan era, Lead replacement of nowadays and of course super unleaded in the way they burn. Suggestions being longer stroke cars such as MGB using unleaded, have a problem as the fuel burns more quickly and has finsihed burn before the ideal time for exhaust cam opening with result of loss of power but excess heat.
Several people I know of here in Greece with older BMW's that have worn out catalysts are going to lead replacement fuel and finding it gives greater progession and lask of back firing.
A friend a Shell in the UK was not able to comment much but did accept that some unleaded contain oxygenates which could burn quiker and also make mixture a bit leaner.
Does anyone have any ideas on this or some scientific evidence please?
Second Gear
Second Gear
Posts: 105
Joined: 06 Nov 2003
Location: WEST WALES

PostPost by: types26/36 » Sun Nov 14, 2004 7:01 pm

I've got nothing to add on valve/seat recession but I would like to throw something else into the debate.
My Sprint and Europa both have BV 126bhp engines in standard trim without lead free conversions, the late Graham Arnold advised U.K. owners to use Optimax petrol and I normally use LRP (lead replacement petrol) with out any problems, I have tried Optimax and can feel NO difference as my engines are quite happy.
The Sunday Times (u.k.) recently did an article under the heading "The wonder fuels that dont deliver"
<a href='http://driving.timesonline.co.uk/article/0,,12389-1289720,00.html' target='_blank'>http://driving.timesonline.co.uk/article/0...1289720,00.html</a>
which concludes that the use of Optimax is of little benifit if any !
I have long since thought the claim's of some owners regarding the extra power they gain by useing Optimax has been more in their minds then in their engine.
Any thoughts and comments? and lets hear from the "silent majority for a change!
If the link does not work do a Google search on "the wonder fuels that dont deliver"
64 S2 Roadster
72 Sprint FHC
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 3887
Joined: 11 Sep 2003
Location: U.K.

PostPost by: andrewdmoore » Thu Nov 18, 2004 12:28 pm


Several years ago the FBHVC commissioned tests on Additives. All those that were proved in their tests to stop valve seat recession are listed on their website. Interesting was the fact that no major fuel company submitted their LRP petrol for tests. Worryingly you are categorically told not to mix additives with different base constituents eg Manganese, potassium, sodium, so if you fill up with LRP from different manufacturers you are probably doing this.

LRP is now not being sold by many petrol stations simply because of lack of demand. Anybody that really cares about their engine buys unleaded and adds an approved additive. Most Lotus people seem to side with Millers with the Octane booster as the twin cam was supposed to run on 5 star.

I'm lucky enough to be able to drive through the Peak District and buy 'Proper' Leaded 4 star from a Bayfield Thrust Garage. Have you checked the FBHVC website to see if one of these Petrol Stations is near you? Apparently this is nearly 5 star RON anyway. If I'm paying ?1 a litre I may aswell use the good stuff!

Regards, Andrew
Second Gear
Second Gear
Posts: 64
Joined: 23 Sep 2003

PostPost by: Rob_LaMoreaux » Thu Nov 18, 2004 12:57 pm


The Octane rating is basically a rating of how fast the fuel burns, so whether the old leaded and the new unleaded work the same can at least in part be determined by the octane rating.

This also shows why the lead replacement fuels and unleaded in the UK may not work as well as the old unleaded. The unleaded fuels seem to have a lower octane rating so with the timing set for the higher octane leaded the engine would have more knock.

My car actually looses power when I add 110 octane leaded racing fuel, since the timing is then wrong for the octane rating of the fuel. My car runs great on 93 octane (R+M/2) fuel which is around 98-100 octane the way the UK measures octane. If I changed the advance when I put the racing fuel in I could get the power back.

So yes the lead replacement fuels may make the BMW with the burnt out catalyst run better, but it it likely that it is because the catalyst was burnt out by the engine running wrong and the LRP is a better match to the timing/mixture the engine is running at.

On a TwinCam the main thing to do when switching away from leaded fuel is to tune the engine to the new fuel since their is no computer to do it for you. On the BMW with a catalyst the engine management system should do that for you.

Fourth Gear
Fourth Gear
Posts: 968
Joined: 22 Sep 2003

PostPost by: types26/36 » Thu Nov 18, 2004 2:34 pm

I agree with what you are saying and I do buy my LRP from one sorce, there is a garage that sells leaded fuel not too far away although I have never used it (I was told by another Lotus owner who uses it that "it goes off very fast") and I dont use my cars very much.
Coming back to Optimax, the point I was making was that it is not "the best thing since sliced bread " or what ever the fuel company would have us believe although some Lotus owners would like to think so.
I do believe Optimax had a very successful marketing campaign and this means big profits for the oil company :angry: .........the bottom line.
Rgds Brian
64 S2 Roadster
72 Sprint FHC
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 3887
Joined: 11 Sep 2003
Location: U.K.

PostPost by: pereirac » Mon Nov 22, 2004 8:47 pm

A thought...
Avgas (Aviation fuel) is 5* Leaded as far as I am aware. It's about ?1.00 a litre in the UK from a suitable airfield??

72 Elan Sprint
87 Excel SE
97 Alpina B10

User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1136
Joined: 01 Oct 2003
Location: Cambridgeshire

PostPost by: rgh0 » Tue Nov 23, 2004 9:13 am

Avgas is typically 110 octane (R+M/2 method) and better than the old UK 5 star was. Also its production is very tightly controlled with regards contaminants ( such as water) and has a formulation to maintain a high stability on storage and long term high or low temperature exposure.

Great for a low use car or a high compression race car. Unfortunately no longer legal to use on the road in Australia and subject to tight selling controls if not put directly into an aircraft. I need a special passbook to be able to buy it for my Elan to use in historic racing.

In God I trust.... All others please bring data
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 8940
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: cdraper » Wed Nov 24, 2004 10:37 am

I wwould just drive it on unleaded. If the tappet clearances need adjusting more frequently than before or you lose compression - have the seats, valves changed - I suspect however you will not have a problem unless you "cruise" at 7000rpm all day.
Second Gear
Second Gear
Posts: 79
Joined: 22 Oct 2003

PostPost by: archigator » Thu Jan 06, 2005 12:18 am

I was a spectator at a Ferrari Challange race a few years ago at the Homestead Speedway, and I asked the factory racing fuel vendor there about the suitability of Aviation fuel (Avgas) on a Lotus in lieu of purpose-designed racing fuel. He told me that the Avgas has de-icers added, and that that might not be such a good thing in a car engine. I don't know if that is a problem or not.

However, I live near the Florida Everglades, and there are certain conventional gas stations in the area that sell high-octane Avgas at the pump to airboat owners whose airboats run on aviation fuel because they use airplane engines for propulsion. It's not unusual to see a few muscle cars on a Saturday morning lined up for a drink as well...

'71 Elan Sprint
User avatar
Fourth Gear
Fourth Gear
Posts: 554
Joined: 15 Sep 2003
Location: Miami (down where the old gators play), Florida

PostPost by: mike+2s130 » Wed Jan 12, 2005 11:29 pm

i use castrol valvemaster plus .it is well known and tested.it is used by most in the classic car world.i use normal unleaded fuel and have no problems.it costs about 10 pounds english and teats about 200 litres.if you use an additive stick to the same one and dont mix them.its the cheapest and safest way and keeps the car original
First Gear
First Gear
Posts: 18
Joined: 10 May 2004

PostPost by: GrUmPyBoDgEr » Thu Jan 13, 2005 8:34 am

Hi there,
I've seen a few of you referring to the possible use of AVGAS in your engines. Please don't do this. I've seen engines that have been ruined in a very short time due to the use of this fuel. AVGAS has a different type of additive package and IT WILL turn your engine oil into sludge.
Beware of the Illuminati

Editor: On Sunday morning, February 8th 2015, Derek "John" Pelly AKA GrumpyBodger passed away genuinely peacefully at Weston Hospicecare, Weston Super Mare. He will be missed.
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 3062
Joined: 29 Oct 2004
Location: Burnham-on-Mud

Total Online:

Users browsing this forum: No registered users and 35 guests