Mono-grade V Multi-grade oil in stationary motor

[TonyC]

Hi All,
I have a Briggs and Stratton 11.5 HP "Intek" motor that's due for an oil change.
It calls for a 30w mono-grade oil.
Why do small stationary motors spec mono-grade oils over multi-grade, and is there any reason I shouldn't use "Penrite HPR diesel 15"

Thanks in advanced.

Tony

[rover-56]

I am interested in this too - I can't see how a multigrade oil could not be better that a monograde.
Oil experts??
Terry

[gromit]

From memory multigrade oils don't like the pressure they're subjected to in roller bearings.
A 20/50 gradually becomes a 20/40 and if run long enough becomes a straight 20. Something to do with the long chain molecules that allow the oil to change viscosity getting broken down as they pass through the roller bearing.

There were always concerns with older motorbikes but if you change the oil frequently enough then it may not be a problem.

I've always tended to stick with what the manufacturer suggests. I did run old bikes on multigrade oil because it saved switching between summer weight & winter weight oils (this was back in the UK). Then I read a few articles that suggested a straight oil was the way to go and by then I wasn't riding in the winter anyway.


Colin

[Hoges]

Very interesting article Multigrade Oil - To Use or Not to Use (http://www.machinerylubrication.com/Read/204/multigrade-oil)
It's to do with the shearing effects to which monograde oils are more resistant. If your B&S engine generally runs in warm weather and is well ventilated to maintain a stable operating temperature, then a monograde oil is the way to go.
I remember having a Morris 1100 which ran on SAE 30 and racked up over 200,000 miles. It didn't like the later multigrade Castrol GTX ...used to sludge up under the filler cap... the #3 cylinder conrod went through the block :angel:.

[mick88]

I think you will find diesel oils are higher in detergent.
Is your B&S engine splash or pressure fed?
Although not B&S, Kohler have a vast range of stationary engines and they recomend either 30 grade or 10w-30 for their engines.
Honda also recomend a monograde 30 for their mower engines but the Caltex recomendation is 10W-30.
Others will have a better knowledge base on the reasons why!

Kohler Engines: Kohler Oil: Parts & Accessories (http://www.kohlerengines.com/accessories/kohlerOil.htm)

Cheers, Mick.

[Hoges]

Further to the above, the following is a very good and simple description of the how multigrade oils work ...Google 'mono vs multigrade oil' and open
[DOC] monograde vs multigrade engine oils - Lubricantsonline.co.za

cheers

[eddy]

I would tend to stick with B&S recommendations.My Intek 14.5hp only lasted 400 hours before something major inside broke.It had regular oil and filter changes as well as air filter changes.I was using Penrite 20/50 four stroke small engine oil and Donaldson P550335 full flow oil filters.Replaced the Intek with a 17.5 B&S Professional ,much 'nicer' motor,only using B&S oil and filters from now on.

[TonyC]

Well it's 5 years on and I find myself looking at the Penrite diesel 15 and asking the same question.
To confuses matters more, Penrite still recommend mono grade SAE 30, but also say Small Engine 10w-50 is ok. Thay don't list a Small Engine 10w-50 in the gardening range, but do have 20w-50 mineral and 10w-50 semi sinthetic as well as the recommended SAE 30 mineral oil.
For what it's worth, Honda recommend Multi Grade for my 4 stroke brush cutter.

WHERE ARE YOU RICK.

Tony

[rick130]

Tony, I used to look after a small fleet of old style side valve and newer OHV Vanguard B&S engines that were in severe service on refrigerated trucks, they'd be running for at least 9 hours a day and we just used the same oil that the Isuzu's used, a 15w-40.
Once oil guard switches became standard we'd get three years at least out of them, well above their projected life.


The reason a mono grade oil used to be called for was that multi grades would shear in severe service. They couldn't handle the heat of an air cooled engine.
Modern multigrades are fine.

[TonyC]

Thanks Rick,
I'll just use the same oil as the 300 Tdi gets then,

Tony

[rick130]

Thanks Rick,
I'll just use the same oil as the 300 Tdi gets then,

Tony

Perfect [biggrin]

[shack]

Wouldn't the presence or absence of a filter change things as well, certainly on the detergent vs non detergent front?

[rick130]

Wouldn't the presence or absence of a filter change things as well, certainly on the detergent vs non detergent front?

Not really IMO.

If things are clean internally and well serviced from the beginning...
A full flow filter does bugger all, it pretty much just catches debris if you have a component failure. Most are up around beta2=25 to 35, which is pretty coarse filtering.
Real filtering only happens with a by-pass filter, and I'd rather have stuff suspended and dispersed so it drains at the next oil change than accumulate and create sludge regardless if the engine is with or without a filter.

In the old days detergents may have created chamber deposits, (metallic ash additives) and race oils didn't and some still don't use them as they can create detonation issues for the same reasons but by and large it's a non issue.