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Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

Generator Oil Change Intervals 3600 RPM Gas


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  #1  
Old 08-03-2014, 10:28:58 AM
Hummer Hummer is offline
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Smile Generator Oil Change Intervals 3600 RPM Gas

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.tpu...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.
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Old 08-03-2014, 10:42:40 AM
Ed Sparks Ed Sparks is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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.
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Old 08-03-2014, 10:48:25 AM
AandPDan AandPDan is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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.
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Old 08-03-2014, 11:59:14 AM
Hummer Hummer is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

Thanks much for info.

What lube weight does it call for?
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Old 08-03-2014, 01:00:22 PM
AandPDan AandPDan is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

It depends upon temperature.

30 wt or 10w-30.

5w-30 below 32f.

Check the attachment.
Attached Files
File Type: pdf Tecumseh Oil.pdf (56.6 KB, 36 views)
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Old 08-03-2014, 01:17:26 PM
Isaac-1 Isaac-1 is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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
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Old 08-03-2014, 02:06:42 PM
Hummer Hummer is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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 104F.

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,-65F to -165F 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!)
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Old 08-03-2014, 09:03:06 PM
Hummer Hummer is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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

Now I am wondering what happens if 10W40 oil is used?
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Old 08-03-2014, 09:21:28 PM
Thaumaturge Thaumaturge is offline
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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
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Old 08-03-2014, 11:57:24 PM
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Default Re: Generator Oil Change Intervals 3600 RPM Gas

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?
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