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Generator Oil Change Intervals 3600 RPM Gas

Hummer

Registered
I have a PowerBack GT5250 w/ 10 hp Tecumseh engine and alas the PO did not have a owners manual for it. The engine only holds 21 oz of lubricant and unit has a 7 gal tank which reportedly runs about 7 to 10 hours on a tank depending on the load.

Thusly, using 8.5 hours (510 minutes) (average) for a run time per tank and dividing that by 21 oz gives a little over 24 minutes run per oz of lubricant.

Not knowing how much testing manufacturers have done with different lubricants, I referred to military standards to get an idea as I am familiar with the test procedures mandated by military lube orders and how much testing is performed under extreme conditions at Aberdeen Proving Ground. I was a Small Arms and Ammunition Test Director there and I have a good idea of the requirements all military equipment is subjected to and is required to pass.

Thusly, I decided to research the lube orders for a 3600 RPM air cooled gas generator:

http://automotiveenginemechanics.tpub.com/LO-9-2805-258-12/0694970002.htm


The MEP017A Generator calls for 2 1/2 qts (80 oz) of lubricant and there is a call out for two lubricants, 15/40 and HD30 and remarkably the hours are literally cut in half when HD30 is used in lieu of 15/40.

15/40 in a 50 hour run cycle (3000 minutes) divided by 80 oz lubricant gives 37.5 minutes per ounce run time .

HD30 in a 25 hour run cycle (1500 minutes) divided by 80 oz lubricant gives 18.75 minutes per ounce.

Therefore as a rule of thumb on all (6) of my 3600 RPM air cooled gas generators I am going to use the military figures instead of those from the manufacturers one of which calculates at over 150 minutes per ounce of on board lubricant.

In comparison to the cost of replacing an engine, high grade lubrication with frequent changes seems to be the responsible way to go to insure long component life in light of the fact that when we really need a generator, the conditions are likely to be extreme and by the nature of the term Emergency Generators seems to mandate TLC to insure reliability.
 

Ed Sparks

In Memory Of
Last Subscription Date
06/28/2015
The rule of thumb for 3600 rpm gensets is oil change at 24 hours or more frequently.
I have several small gensets for job-site use and they get oil changes at 15-20 hours usage. Most of them are older sets that I recycled after dump picking or cheap yard sale units. Most I've paid was $25 for a 11 hp 5500 watt that had a broken pull cord and needed the carb cleaned. I use it to run our camper when off grid at our land up north.

You are correct most of them only hold ounces of oil compared to our Onan's with quarts of oil. Always use the best oil you can to get the longest life out of them. The Chinese clones seem to be susceptible to throwing rods when used with poor oil maintenance.
 

AandPDan

Registered
The Tecumseh L-Head Service Manual, you might be able to download a copy, indicates 25 hour oil changes.

If you don't have a low oil shutdown on the engine, be very careful monitoring the oil level until you know the consumption.
 

Isaac-1

Registered
Last Subscription Date
01/12/2014
Regarding that military reference, keep in mind that the MEP-017a was built 45-50 years ago, and engine oil formulation has changed a lot in that time.

Ike
 

Hummer

Registered
Ike, couldn't resist reply but I was built 67 years ago and my chassis is tired, my on board computer has dust on floppy disc. And other things don't match the original design issue either haha.

For sure the synthetic lubes are far superior to what they were back that time frame.

I can't remember where I read it but there was something the other day that said the -40 lubricants were needed for high temperature runs in generators. One of my units says not to operate over 104°F.

I well remember a conversation I had with a owner of a electric motor rebuild facility in Columbus, Ga about 1994 and I asked him about lubes and he said he used nothing but Mobil 1 for previous 22 years and had never had a motor come in for bearing failure with Mobil 1 in it.

I had a attic fan in my shop and was out there when it started making a awful noise and before I could turn around the motor froze up. I killed breaker quickly and after research determined the frame size could only be obtained in a part of the world that was yet uncharted. I put Breakfree in it and got it going. Lasted several days and siezed again.

I remembered the Mobil 1 lecture so I pulled it down. It had become so hot some of the internal parts had turned blue. I laid the Mobil 1 10W30 to it and it was running just fine a year later when we sold the house and moved home to SC.

I just went back and checked the lube order and it is dated April 1992. It superseded one dtd 1989. If one could get the drawing package it should give the revision number. There are times I wish I wasn't retired as I had access to all the tech data I could ever have hoped to read.

I remember a conversation with another Test Director at Aberdeen and he said the generators were all placed on a island in the bay and hooked to a dummy load and fed from a large fuel tank and they ran full load 24 hours a day.

The vehicles were driven 16 hours a day and third shift did maintenance and measurements/repairs on them so they could be back and running 0800 the next morning. After a Aberdeen test when the reports go out there is often engineering changes made. I remember when I was there a series of trucks from Germany were being tested and the frames holding the fuel tanks broke dropping the tanks in front of rear wheels.

On military vehicles the requirements for the tactical vehicles were 25,000 miles and it is the worst 25,000 you can imagine. Dirt, pavement, Belgian block, up/down 60° grades and alternate humps that flex frames, mounts and water submersion,-65°F to -165°F etc. The dirt roads are constantly being regraded to match the orginal test track laid out when the Proving Ground came on line. The idea is they want everything tested just the same year in and year out with as little change as possible. For instance propellants in ammunition has changed over the years.

Our unofficial motto was,"You make'em we break'em!)
 

Hummer

Registered
Wow, great info on the Tecumseh line in general. Many thanks.

Now I am wondering what happens if 10W40 oil is used?
 

Thaumaturge

In Memory Of
Age
68
Last Subscription Date
07/12/2019
I can't help but jump in here with my $0.02. I live off grid. Run a generator between 10 and 14 hours every day. What I've found is that how often you need to change oil depends heavily upon how much dust and dirt is around. Fist thing to do is to epoxy a good powerful (N42) magnet on your drain plug. You'd be amazed at how much fine metal crap you will find stuck to it when you change the oil. Next trickis to get the generator up off the ground to reduce the amount of dust and dirt it gets subjected to. A recent study sugests 3-4 feet, but just up on a pallet makes a noticable difference. My current generator has the best longevity record out of about half a dozen. I change oil a minimum of once a week, but usually twice. No biggie as it only holds about 1/3 quart. What I did different on this one (and the ONLY thing different) is that after the third oil change (to give rings a chance to seat properly) I added about a teaspoon of pure Molybdenum Disulfide powder to the fresh oil. Just that one time treatment has over doubled what I was getting for average life. Model I use has a nylon camshaft that would suffer fatigue failure on the gear teeth right about 1050 hours (+/- 50). Four identical units died after that same interval. Current identical model has between 2500 and 3000 hours on it after that one moly treatment. Think I'll stick with that formula. Mentioned generator is a UST 1250W 4 stroke from Wallyworld. (about $200). The reason I run them rather than a bigger one, is because they run up to 14 hours on a 1.3 gal tank. I've got larger gens I run for power tools and welder, but mostly I;m focused on economy.

Anyway:
Magnetic drain plug, cleaned every oil change.
Change oil more often in dusty environments.
Get gen off ground... up on a pallet or even just on a piece of plywood to get away from dirt.
Lastly, after break in, a one time treatment with Molybdenum Disulfide. If you can't find a source (I've had my bottle since high school in the late 60's) try to find a bottle of "Slick 50". I'd run it full strength for one change cycle, then just good quality oil. I run Castrol, as I learned it was good oil for air cooled engines in my VW days.

Probably closer to $0.08 but all based upon actual daily experience.
Doc
 

Hummer

Registered
Doc, I concur completely with the moly additive. Had not thought of that and I have at least a pound of it. It's perfect for a splasher as well.

There are two variations of moly powder, inhibited and uninhibited. I have run it in differentials for years and also have mixed it with Mobil 1 on occasion for electric motors.

Inhibited is best for applications where galvanic action may occur and last I heard it was like 35.00 a pound where the uninhibited is much less expensive.

Will do that this coming week. Kicking myself for not thinking of it sooner.

Where did you get the little magnets for the drain plugs?
 

Thaumaturge

In Memory Of
Age
68
Last Subscription Date
07/12/2019
Where did you get the little magnets for the drain plugs?
Take about three weeks to arrive, but I've dealt with them for several years now and have received everything I ordered. The shipping delay is due to new airline regs requiring all air cargo coming out of China to be X-rayed. Since about last September, really has things backed up. What used to take ten days now takes three weeks to a month. They (dealextreme) take paypal, which is the only way I've dealt with them.

http://www.dx.com/p/5-x-5mm-cylindrical-ndfeb-magnet-silver-30-pcs-248292

Might find equivalents on Amazon. Trick is to find some just smaller than plug thread. Picked up the trick in my VW days. But practice is now widespread enough they just magnetize the bolts on most new cars.

As to my Moly, don't know what type I have. As I said I'm working on the tail end of a big bottle I was given in about 1967. Somehow managed not to break the real glass bottle after all these years.

As it was explained to me, the molybdenum part forms an ionic bond to any steel parts and then the sulfer part shears like a graphite whenever you would get a metal to metal condition, such as lubricant breakdown on sleeve bearings. I attribute the extended life of my current nylon camshaft motor to reduced back pressure on gear teeth from lobes, reducing material fatigue on the nylon gear teeth.... or I just got a fluke lucky cam...
Doc
.
 

Hummer

Registered
I learned of Moly when I attended a course at Rock Island Arsenal in 1985 called Corrosion Control and Prevention of Material Deterrioration and a full day was dedicated to educating us about it. The only place I know where inhibited is sold is Sandstram Inc Port Byron, Ill and the powder was referred to as 532. Many of the M16 rifle parts are coated with it to prevent corrosion. In that application it holds up better than chrome in a salt spray environment.

The first application the gov't used was the 9A and this requires heat curing at 300°F for I believe it is an hour. With everything else it has gotton much better over the years.

Now they have some stuff called 28A that is painted on and I have been running a test. Bush hog mowers have a tail wheel that takes a 1" diameter bolt as an axle. The original wore out first season and was greased prior to every use.

I got a new 1" Grade 8 bolt and turned new bushings for inside of tail wheel and used 27A on the bolt and bushings and absolutely no grease and I could mow with it for like 8 hours. I simply removed bolt, re- painted the surfaces where it was removed and the bushings and put bolt back in after they dried and this was done for four years. Then about 15 months back I got some 28A and now I can mow for 12 hours. The conditions here are bad for such application as the mower has a rear discharge and the axle/hub are constantly bombarded wtih blowing sand yet it keeps on going.

I was going to use 28A to coat the threads on my Onan generators prior to adding additional muffler but I don't know the temps the mufflers see and when I pull out the MEP017A for it's monthly run I am going to load it up and check muffler temp with infrared thermometer. Not sure of the data but was told gas engines heating catalytic converters don't go over 500°F.

http://www.sandstromproducts.com/pdfs/e728.pdf

I have noted the threads develop corrosion quickly and I want to be able to unscrew the 1 1/4" elbow I am going to put on it otherwise it will sieze for sure.

I was thinking if it is not too big of a job you could remove the camshaft and paint it with 28A but it would appear you have found the right combination now.

I do know for sure do not use graphite on ANYTHING. Back in 80s they removed it from about 98% of the gov't grease. As well some of the first moly grease did not utilize inhibited moly and there were bearing failures with it.

Should anyone want to know what is so bad about graphite I have typed up a excerpt page from the manual issued at Rock Island for the course. It is several pages long and an excellent read. If anyone would like a copy PM me a email address and I will send you a copy in Word. For the legal types it is from a gov't publication and they are considered public information and not subject to copyright law.
 

Hummer

Registered
To the person who just sent me a PM for the graphite article , I just sent it to you at 1352 hours.
 

Thaumaturge

In Memory Of
Age
68
Last Subscription Date
07/12/2019

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
Change oil at 25 hours for most air cooled engines. Check oil level EVERY fuel fill up and engine start! DO NOT USE ANY OIL MARKED 'ENERGY SAVING', or oil made for modern automotive use (read newer cars) Use either an oil made for small engines or a diesel rated oil like Rotella T (TM). Diesel oil is OK to run in gas engines, and has the high pressure lubricants these engines need (MDS). Automotive oil sold today is no good for small engines. Especially the Chinese junk and others that are using plastic cams and small high load componants (read small OHV engines), they need all the lube they can get. I have heard of Mobil 1 being used in small engines, but probably not as cost effective as a diesel rated oil, and synthetics will find any leakage points quickly! NOTE: When using a multigrade oil, a large bore single cylinder engine (5 HP & up) WILL burn a certain amount of oil, as the swept area of piston and cylinder expand with the engine function. Air cooled engines run at temps approaching 3 x the operating temps of a liquid cooled unit. It is important that the oil level be checked at every start, especially if the unit is heavily loaded.

Having been in the small engine service industry for over 50 years, I have found the following is a must: Clean air filter, clean FRESH fuel - not more than 30 days old, clean and full oil level, regular oil changes, and if at all possible, a clean working environment. All the above will lead to a longer service life of your unit.
 

Thaumaturge

In Memory Of
Age
68
Last Subscription Date
07/12/2019
Started doing some research and apparently moly additive oils are already here.

Slick 50 has been around for several decades. Problem is they add less than a quarter teaspoon. Probably fine for a long term treatment. But I start with a half to a heaping teaspoon when I do an engine treatment.

In ref to post about oil types for air cooled engines; Castrol has a long history in that application.
Doc
 

Hummer

Registered
I was under the impression the slick in slick 50 is actually Teflon and not moly?

I was just reading their website day before yesterday and they said it had Teflon?

I wouldn't mind trying some of the German stuff.
 

Thaumaturge

In Memory Of
Age
68
Last Subscription Date
07/12/2019
My mistake. After reading on their site I must concur. Guess I was thinking about some other treatment. But I did find other Moly treatments on Amazon that were much cheaper than $40.
Doc
 
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