Petrol oil ratio

[Bob Purton]

If there are any schmitt drivers looking, what oil/petrol ratio are you using in your cars, I have been using 25 to one but am thinking of reducing it a little.

[Peelpower]

I  use 40 to one since more than 25 years, Never ever have had any problems.

[marcus]

When I had my Velorex with its 2 stroke Jawa 350 engine I started at 20 to 1 as recommended by Quickstart motorcycles. It made a lot of smoke, and the lads at the Motorcycle shop in our yard suggested I try Rock synthetic oil at 40 to 1, and this was a big improvement.

[Bob Purton]

Thanks Ferdi/Marcus.
I have been driving mine for the past ten years using a 25 to 1 mix
I never really thought about it much until someone behind me last year complained of the smoke! Looking back I probably was advised to run the engine in on this ratio and them drop down to something lower once run in and just forgot about it. I think I will try 35 to 1 and take it from there. I'm not sure about putting rocks in it though Marcus!

[Big Al]

Originally quite a few cars were run on ST/SAE30 mixed into the petrol as two stroke was not always available in the mid 50's - see the manual which acknowledges this. That needs to be 25:1. Early two stroke was better but still best at 25:1. Then the synthetics started coming in. Now I had a long talk with a guy who worked at Esso Rerearch about oils. He pointed out that the synthetics have carrying oil that just burns off to apply the active lubricants into the engine. Thus it is not possible to directly compare synthetic with mineral two stroke as you need to know the specification and ratio of carrying oil to active ingredients - does one suspect cheap synthetics as being 'weaker'? Secondly synthetics were introduced primarily as modern two stroke engines tend to run on needle bearings rather than bushings. The lubrication requirement is different. This would suggest that you can happily run synthetic in a modified engine with needle big end, possibly easing the mix ratio out to 40:1. However if you are running a standard top end bush then expect wear to increase and in preportion to the lessoning of the ratio of oil to fuel. I am happy with getting bulk old fashioned two stroke in, it can be found cheap if you shop around. Far cheaper than synthetic so I doubt the financial saving of running a lean synthetic mix to well bought standard stuff. This leaves the whizzo guys. You are on your own with synthetics unless you can get the spec and work out the equivilant ratios to the original stuff available in the '60's. People like Andy Woolley have the patence to test there modifications and work out the optimum settings through out the car. For all the 'I used it for years' chaps I suspect there are quite a few early rebuilds as folk got a bit ambitious with weakening the ratios off. We tend not to hear about those guys as they cocked up.
A smokey stroker once warm suggest a problem within the engine or set up rather than something wrong with 25:1 mix. Oil seal failure is good fun if you like the Navy, smokin'! Wrong mixture in the carb or airleak on the carb flange when the ali shears within its structure of the casting (Bing carbs are pretty crap) will produce smoke, especially after a bit of traffic jam work. An air filter full of oil will bleed into the induction and is a symptom of poor timing spiting fuel out of the carb into the filter container where the lighter parts of the fuel evapourate leaving a pool of oil. Again low revs will show smoke. Lack of use allows the oil to settle to the bottom of the tank creating a heavy ratio of oil and later a weakened one unless there are some bumbs and bends to mix the fuel up. Often a cause of seizure on a first run of the year for no obvious reason. Of course the in-line fuel filter has an effect too as oil is bigger than petrol so takes longer to get through the filter. Indeed I ditch in-lines as soon as possible as they make the car run badly. Better to stick a polymagnet the other end of the tank from the outlet to catch rust from suspension in the fuel if you have a poor tank.

[Bob Purton]

Thanks Threadbear for that, [who are you by the way?] you seem to have thought it through more than others. I remember the good old days when I ran my Ariel Arrow on SAE 30. Never gave any problems but would stink something awfull! I had a word with Andy Woolley earlier and he uses 40:1 with mineral oil. I have a steel conrod and needle rollers so I think I'm ok with synthetic and I always use a know brand primarily silkolene. All my oil seals are good and the carb is well tuned. You may have hit on it when you mentioned oil settling during periods of none use, as I remember the smoking was last year early spring when it came out of hibernation. It eased off with subsequent refueling. I dont use an in line filter because they are nothing but trouble and I dont need a magnet as I sealed the tank with flowliner some years ago.[I have used it in all my cars and bikes, great stuff, I recommend it!]  It was interesting what you found out about the nature of the oils, part carrier and part lubricant, I guess most synthetic oils are designed for autolube systems. Well, I have decide that this year I'm sticking to synthetic and will try 35:1. Interestingly my little Tomos moped [the only moped to be sold by Woolworths!] uses a 50:1 mix, now that is lean!

[marcus]

Interesting post Thread Bare, and Bob: is Flowliner for petrol tanks? 4 strokes? Where from and how much? Ta!

[Bob Purton]

Hi Marcus, Its a tank sealer for two and four strokes available from Wyldes Motorcycles http://www.cwylde.co.uk/
After I restored my Schmitt I was forever getting a bunged up carb with tiny powdery rust particles, I used the afore mentioned product and never looked back. I'm told that POR15 is also good but steer clear of petseal. Its ok on cats and dogs but no good in fuel tanks!

[marcus]

Cheers Bob. Yup rust in tank has put DUF off the road, cut it open and gave it thourough clean ou, now waiting for friend to TIG weld it up (my welder is not controllable enough for that job! Once welded and sealed and with new battery I will be on the road again, hopefully this millennium!

[Big Al]

I would be interested to know if these fuel tank sealants are OK in Germany, for instance. I had a Saab that lost its sealent because the fuel is differently formulated over there and dissolved the stuff. Fortunately when I was back in Britain but the cars tank and system were a total mess. So either some comfer mation or a bit of testing required perhaps or if you have been abroad and start suffering issues worth a check to see if the sealant is in place. My treated tank was inherited so I cannot tell you which product it was. I can tell you that the RAF fuel sealent for aircraft is utterly brilliant. However it is very expensive and the SAS are still after my naughty bits for taking some so I cannot yet reveal who I am but I know and have met just about everyone on this site so far so its not a huge surprise!
I forgot to mention that increase the oil ratio to, say 20:1 is a bad idea. In fact this will result in a weak mixture and carbon (smoke). If in doubt less oil is better than to much as the engine will normall tinkle with heat before it nips up. So listen to the engine, it often tells you what it is up to. If so you can increase the fuel flow or bung a little more two stroke in. Do not play Tuxedo Moon at high volume on the Dutch motorway as I did once after filling. It sounds much the same as a seizure and I only realised something was wrong when the rear wheel left a skid mark about 20 foot long. I had forgotten to put in any oil at all. Had to re run the engine in after that to clean it up and buy some new trousers to clean me up.

[marcus]

On a bit of a tangent, but I have a question for you Thread Bare, as you seem to be clued up about fuel etc..
A couple of years ago I was driving down to Kent and noticed a distinct smell of Avgas / jet aeroplane engine fuel. I have flown a lot from an early age and I am absolutely sure that it was Avgas, that unique smell of big airports.
For several miles the smell grew stronger until I finally overtook two modern Army personnel carrier trucks, possibly AWD. We stopped for a while, then later caught up with them and their smell on the road to Rye and Hastings. The engines sounded like piston engines, but others in my car agreed they could smell "airport" coming out of the trucks. Any ideas?

[Bob Purton]

About continental fuel, funny you should say that, a friend of mine did the Moto Giro Italia, he returned with a big patch of paint missing off his tank, the whole UK party also had fuel damage to the outside of there tanks due to ferocious Italian petrol. A spillage of UK fuel if wiped off did not damage at all whilst the foreign stuff was pure paint stripper!

[Big Al]

I am no engineer, I learnt at the side of the road, nor am I a fuel expert. If I do not know enough about a subject I believe in asking someone who does. In fact I really wanted to know about why you should not use multigrade oil in a Heinkel engine. We digressed onto the Schmitt as it was there.
Why would Army personnel carriers be using avgas? I can only guess that they were powered by an aero type engine as that offered the greatest power from the space available for the engine. It would make even more sense if they were American manufacturer. If so this is drifting toward an error the Germans made in the second world war. They had the best armoured weapons but each was specific in spares, amunition and fuel requirements. This was fine until the battle front expanded into a huge area or air superiority was lost. The Russian approach of standardisation and numbers defeated quality and specialisation. A look at the 'wars' we are fighting at the moment rather bare this out. The best equipment does not really defeat an informal army who use relatively simple weapons imaginatively but is fine against an inferior traditional army. The fact we need loads of helicopters suggests we are not winning. So we have a swat not a bleach. Quite why we thought we could do what the Russians could not defeats me but I forget this was not a war of choice but a corparate one created by the two B's in charge at the time. So this question now becomes pertinant since I would point out that the Navy is only just bigger than the MOD department that is responsible for it's procurement. So who controls what and where is all the money going? Not on soldiers! I do not feel as safe in Britain as I did 20 years ago knowing this. That is a political question worth looking at given the disinformation from the political leadership. All this from smelling avgas.
Alternatively they were moving RAF personnel in some sort of exercise with the windows open.
You can run a Schmitt on kerosene and paraffin. Parafin needs tickling with petrol to start really. Cannot recall doing so with kerosene but the engine might have been hot. So you can bung a 50/50 Parafin/petrol mix in and the car will go, but not as fast. Perhaps we ought to slip some into Andy's car so we can keep up. Heinkels will run on white spirit, well to get off a motorway to avoid a blood wagon call out they will! Oh to be an impoverished Microcar owner in the early '80's.

[RalphT]

The smell of Avgas was because the vehicles had diesel engines that can run on Avgas.

[marcus]

Cheers! Is Avgas cheaper and/or give more power than diesel? Can I run my transit on it?
If we can run our Heinkel/Trojans and Messerscmitts on it that would be a nice link to their ancestors!