Which is the best oil Multi or Single Grade?

[LowNSlow]

My knowledge of oils consists of the following:

a) Assisting to get it out of the ground pays for my mortgage and flying.

b) Multigrade oil is recommended for engines that experience major ambient and / or operating temperature variations ie cars going from stone cold where they need the low temperature low viscosity characteristic of a multigrade to reasonably hot cruising down the motorway when the high temperature high viscosity characteristic kicks in.

c) Single grade oil is recommended for engines which operate in a reasonably constant ambient temperature and/or at a reasonably constant operating temperature ie fixed engines powereing generators etc operating in an enclosed environment and running at more or less constant speeds and temperatures.

Bearing in mind the above why do we operate our engines, which experience a wide range of both ambient and operating temperatures as per b) above, predominantly on single grade oil?

Also puzzling is that some of the new models of Lycoming engines, although based on older engines are recommended to run on multigrade whereas their descendents still use single grade.

Is it because most of them were originally designed before mutigrades were thought of and we’ve stuck with the same standards because the licensing authorities say so?

Is there something about modern multigrades that would be the kiss of death for an old engine like my Cirrus II (1946 vintage)?

As a great believer that regular oil changes are a lot cheaper than replacing run out bearings and crankshafts I would like to prolong the life of my engine as much as possible. Any engineering bods out there who can point me in the right direction of the best oil to use in my aged engine?

[Windy Militant]

LowN slow,
Get in touch with the nice people at AeroShell we had a very interesting evening at one of the PFA struts I'm a member of, where the nice man explained it all and offered advice on running various types of engine including storage tips for when your not using the aircraft. There are various reasons not to use multigrades in older engines but I believe that the main one is to do with the larger clearances between components which with a multi-grade which is less viscous when cold is more prone to oilshear and blowby than the straight oil which is thicker Although I Stand to be corrected by the experts out there on this

[LowNSlow]

windy_militant , hadn't thought of that one. From a fluid dynamics point of view I can see the point.

The fact that the AeroShell man is admitting there are sections of the market they can't sell their multigrades to does lend credence to their statements. I was going to ask them at the PFA Rally but there was never anybody on their stand when I walked past....I'll have to get in touch with them to get the info.

I suppose it depends on what the clearances on old versus new bearings are. From my dad's descriptions of the clearances involved in the crank bearings of his beloved WW2 era Bristol Hercules radials they were on a par with anything one is likely to find in a Lycoming or Continental crankcase :D

Must check out how the clearances on a Cirrus crank (designed in the 40s) compare with that of "modern" engines say an O-320 (designed in the 50s) or an O-200 (designed in the 30s). :D :D

It also backs up the old 2nd hand car dealer (sorry, purveyor of fine pre-owned vehicles) trick of putting heavy weight oil in worn engines to stop them rattling on a cold start :D :D

Edited to remove cynical hat :D

Play the Amoolia Earheart Flying Cow game at www.aeroshell.com
it's a moo :D :D

[FlyingForFun]

But LowNSlow, that hat suited you! :D

FFF
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[LowNSlow]

Why thank you FFF :D

[javelin]

Having operated various aircraft over the last few years and after long discussions with oil suppliers and engineers, here is my two penneth.

If your aircaft is used regularly, has low hours and doesn't stand idle for days or weeks, then multigrade may offer a benefit. However if like most of us, you don't use it regularly etc, single weight detergent oil gives better protection against wear and corrosion when stood.

I recently saw several engines in for overhaul near here, all were large engines run on multigrade but not used regularly - they had all been snagged for metal in the filter and guess where it came from - the camshaft at the top of the engine which is the first to drain off and corrode.

I change the oil every 10 - 15 hours with no filter, 20 hours with a filter - it is the cheapest maintenence you will ever do to your aircraft and can nearly always be done by yourself and signed off by yourself.

[str12]

A few years ago I started using an oil treatment (not an additive) on my cars and motorcycles and was impressed with the results.

It works by coating the moving parts with PTFE - a VERY slippery substance. In fact, the literature quoted engine friction being reduced by up to 80 percent and the piston rings in your car probably have a PTFE coating already.

Starting on a cold winter's morning meant the engine would turn over immediately. There was also a small reduction in fuel consumption and a slight increase in horsepower. The literature also mentioned longer engine life etc.

Should a complete loss in oil-pressure occur then a large reduction in friction would keep the spinny-thing spinning longer, give you more time to deal with the situation, reduce the chance of a catastrophic component failure and generally reduce the overall 'sphincter-factor'.

I was wondering if there was somethig similar for piston aero engines as there would be obvious benefits?

Cheers.

[A and C]

Ther are two types of multi-grade on the market the first is the mineral oil such as Baker ,castrol and BP sell and the other is a semi-synthetic oil that shell sell

Some of the problems stated above with regard to low usage engines might be leveled at the mineral oils but the fact that these oils flow at low temp and provide effective lubrication from the moment that the engine starts turning must be a major advantage.

The Shell multi-grade is by far the most advanced oil on the aviation piston engine market and should not be confused with other multi-grades this oil has included in it the anti scuff addative that Lycoming recomend for the engines that have camshaft problems it also has an anti corrosion addative , when ever I look inside the the rocker covers on my lycoming O-360 I never find any corrosion , you wont find that is the case with any other oil.

I would recomend this oil for all modern engines that have a low usage rate for older engines Shell have started to produce W100plus and W80plus this has the anti scuff and anti corrosion addatives in it .

These are the oils are the ones that are on the european market at the moment i am sure that american readers will have something to add to this thread.

[circlip]

intersting read


http://www.vtr.org/maintain/oil-additives.html

[Lost_luggage34]

Excellent thought provoking thread LowNSlow - still scratching my head.

I have always carefully considered oil in car engines but never the aspects too much in an a/c engine, apart from level, deposits and the like.

[LowNSlow]

javelin, str12, A and C ta for the advice. When I visited the AeroShell website I noticed the "plus" versions of their 100W oil. I didn't realise it contained the solution to the Lycoming O-320H(?) model "chocolate camshaft" problem. As I work a 28 days on 28 days off rotation my wonderplane sits around for a month at a time and any oil that offers extra protection to the engine has to worth the extra pennies. Especially useful would be camshaft potection.

I think the local AeroShell rep will be getting a call from me when I get home.

str12 I think the CAA would have something to say about unauthorised friction reducing additives in aero engines. This would be particularly relevant to new or top overhauled engines that rely on controlled friction to bed in the piston rings. I have used the additive you refer to but I have my doubts about teflon surviving in the 12-1400 F environment which exists at the piston crown. At the bearings there may be a benefit (seen the blurb about driving for 200 miles with no oil in the sump) but I do have my doubts being a cynical ingeneir type chap :D Basically, I feel if it was that easy it would be in universal use by engine manufacturers. Whoops I can feel a Big Oil conspiracy theory coming :D :D

circlip followed your link after posting the above. Excellent read and firmly puts the oil additive makers into the "snake oil"category.

[str12]

Interesting article, ithas put me off additives. I always use high-quality oils and will stick to that.

Interesting that the articles indicates that damage done by using additives would appear over the long term - just what Slik 50 says it reduces, b@stards.

LowNSlow, I would never do anything to an aero engine unless it was formally approved by the manufacturer, I was just asking a question.

Hope the cars/bikes I've treated in the past are still doing ok...

[LowNSlow]

str12 didn't mean to suggest you would old chap(?) :D

I think the old Mini I put the Slick 50 in has long since gone to that great scrapyard in the sky ;)

As an aside but similar, what about these petrol additives for cleaning carburettors, fuel injectors etc? Anybody seen any tests on those?

[Croqueteer]

I used slick 50 in an old aerobatic biplane that did not have inverted oil and over 9 yrs of aeros and competitions, never had any metal in the filter. I am just reporting this as a fact, it may have had nothing to do with the Slick 50.

[circlip]

THINK TWICE BEFORE YOU ADD THE ADDITIVES
The companies manufacturing fuel additives must be doing a terrific job marketing their product. This has to be the case since so many people seem to want to add something extra to their fuel tank.
The best thing to add to your fuel tank is simply good quality fuel … and nothing else. Yes, I did say no additives. There is nothing better than clean, high quality fuel in a clean tank.

Almost all fuel contamination problem is related to water in the tank. It is virtually impossible to keep it out but occasional maintenance on the tank will get rid of it. Maintenance of the fill cap o-ring will keep most water out. Running out of fuel (or pumping it out of the usual fuel line) does not get rid of the water on the bottom of the tank. An effort must be made to get the water out of the lowest point of the tank.
I guess most of us like what's easy, sort of like a Diet Coke with a Big Mac. It doesn't work.
There are many believers in additives. I've have heard people say, "I've been using Brand X for five years and have never had a problem". Perhaps that was a water free tank that needed no additive. The fuel makers say that they put the right stuff in. The additive makers (all of them) say that you have to use their product. If your fuel has no problem, leave it alone. If it does have a problem, get it out of there and put in good fuel. Good fuel is the second most important thing in Engine maintenance, after the lube oil.
I know that too much of the wrong additive can cause problems. There is word that some additives react with other additives. I personally would rather play safe and keep my tank clean.

It seems foolhardy to me that many owners gamble with a ten-euro jug of additive to try to resurrect fifty euro worth of fuel when the heart of a twenty thousand euro engine is at stake.

[FlyingForFun]

Also, regarding additives which claim to clean things, such as those you mention, LowNSlow. I would be very careful about using these on a car. I would certainly never use any of them on an aircraft.

They may well remove the crap from the carb (or the radiator or any other part of the engine or ancilliaries which they claim to clean). But where does the crap go after that? Straight into the engine! It would be shame to ruin a perfectly good engine all because you couldn't be bothered to have your carbs removed and cleaned properly.

(I have only ever used these cleaners once - I used a radiator cleaner on a very old car which was due to be scrapped soon anyway. Worked a treat - temperatures went down and stayed down until the bodywork forced me to scrap the car. I never bothered dismantling the engine to find out what happened to the limescale or whatever it was which was blocking the radiator previously though.)

FFF
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[skygazer]

Also worth thinking about - the tank from which you pump the fuel in the first place. One would like to hope that the various airfield operators keep their storage tanks in good condition(?!), but for those aircraft authorised to use mogas, then you probably need to be even more careful.

I had a problem about 5 years ago when I filled my car up from a filling station next door to my office. The car ran like a pig, spluttering, misfiring, etc. At first I thought I had inadvertently put diesel in the tank, but talking to colleagues, they were experiencing the same thing, having used the same petrol station.

My car was due in for a service anyway, and when I picked it up, the workshop had kept the old fuel filter to show me. It was full of bits of scale, and also some other junk. When I told them where I had filled up, they weren't surprised. The filling station was not one of the 'big name' companies, but was a small independent operator who was free to buy fuel from any supplier.

The service workshop reckoned the petrol station was buying contaminated fuel on the cheap because no one else would have it, or their tanks and tankers were rotting away inside, thus contaminating the fuel. Needless to say I didn't use the petrol station again, and didn't have any further problems like that.

Of course, everyone checks their fuel before they go flying. Don't they?

[gasax]

I don't have any specific Cirus experience but my Gipsy has towed me around for a few hundred hours.

Gipsys are restricted by AD to 100 grade oil in the UK - the issue is the inverted cylinders which naturally tend to much increase oil consumption. The thinner grades lead to heavy plug fouling and pre-ignition. None of which is really an issue in horizontal engines.

But I think there is a huge element of certification costing in the oil recommended - which of course is why our ancient machines are only certified for straight grades.

There is a powerful argument for using multigrades if the engine is regularly used. If it is not then the heavy straight grades will delay corrosion - so long of course as they are not loaded with debris or acidity - which neatly brings us back to clean oil!