Hello,

I remember reading in my lawn mower (Briggs & Stratton 4HP) that the recommended Oil was SAE 30.
But I think I remember reading  5W-30 was also acceptable.

I cant find the manual, so does this sound right to you guys?
Can I use 5W-30 in my Lawn Mower engine?

Thanks for any help you may provide!

From the manual

Oil  Check oil level regularly: fill to mark on dipstick. DO NOT OVERFILL.
Use Briggs & Stratton SAE 30W oil above 40?F (4?C).
Change oil after first 5 hours of use, then after every 50 hours or at the beginning of the season.

www.briggsandstratton.com/display/router.asp?docid=64394

I have always been told that if you have a splashbath oil system you should use a non-detergent oil. This allows the dirt particules to settle out and stay on the bottom of the case.

The detergent oil will  hold dirt particles in suspension and cause more wear. Detergent oil should be used with a filter system

SAE 30 is all you need.

I just changed my 6 hp Briggs to 0w-40 Synthetic atv oil made by Amsoil. (its all I had on Hand)

Anyway it no longer smokes while it is running and it starts on the first pull,Im impressed.

The idea behind straight 30-weight oil is that lawn mowers are only used during the warmer seasons.  This reduces the need for the lower viscosity, multi-weight oils required during cold weather.

Remember that 5W-30 is a 5-weight oil that thins only as much as a 30-weight would at higher temps.  In other words, it has the viscosity of SAE 5 at lower temps and the viscosity of SAE 30 at higher temps.  It still thins, just not as much as a straight 5-weight would.  The "W" signifies the oil is suitable for winter use.

Motor oil manufacturers acheive this mutli-viscosity characteristic by adding long-chain polymer molecules to the oil.  When cold, these molecules "curl up" and present a low resistance to flow.  As they heat up, these molecules "unfurl" and present a much greater resistance to flow, thus lessening the amount of drop in viscosity.  This is true for the conventional multi-viscosity motor oils.  I'm not sure if multi-viscosity synthetics use the same technology.

I'll make this real simple... Use straight 30w oil in your mower. Buy a good name brand and change it regularly. Not having a filtered system, the only way to get rid of the contaminants, is to change the oil. Run it up a bit to stir things up, then either remove the drain plug or turn it up on its side, dipstick down.

Thanks for all your help guys.

Anyone know of a full syntheic SAE30 oil? I never can seem to find any.

Quoted: Thanks for all your help guys. Anyone know of a full syntheic SAE30 oil? I never can seem to find any.

I've never heard of one, but be sure to check the following makes:

Amsoil
Mobil 1 (doubt it)
Red Line
The Purple Stuff (can't remember the name)

Synthetic in a lawn mower is kinda overkill, IMHO.  Use SAE 30 and keep it changed once or twice a season, depending on how long your grass cutting season lasts.  Make sure it doesn't drop much below the "full" mark on the dipstick and do not overfill.

It's just that simple.

AFAIK there isn't a straight weight synthetic oil on the market. If you are looking for your mower, don't waste the money. By a name brand at $$1.25 a quart and change it every 25-50 hours. If you are looking for it for your ride, buy 10-30 and change at intervals suggested by the manufacturer.

Quoted: I have always been told that if you have a splashbath oil system you should use a non-detergent oil. This allows the dirt particules to settle out and stay on the bottom of the case. The detergent oil will  hold dirt particles in suspension and cause more wear. Detergent oil should be used with a filter system

This is correct.

I worked, once upon a time in another life, at a small engine shop. Non-detergent oil is the type you really want to use in a splashbath oil system.

Use the detergent oils only if your engine has a filter.

I like using Mobil 1 in small engines.

Quoted: Hello, I remember reading in my lawn mower (Briggs & Stratton 4HP) that the recommended Oil was SAE 30. But I think I remember reading  5W-30 was also acceptable. I cant find the manual, so does this sound right to you guys? Can I use 5W-30 in my Lawn Mower engine? Thanks for any help you may provide!

yes, won't hurt a thing

You do NOT want to run a nondetergent oil in your engine. ND oils are the most basic oil you can get, might as well run cooking oil. Whatever you do, ignore the manual. I fail to see what is so hard about this, there is a little chart inside the owners manual that states the CORRECT oil for your engine.

Every time I see one of these oil threads come up, I promise myself to stay away, guess I'm a sucker for punishment.

Honda recommends good 'ol 10w-40 in their mower engines. Check your manual.

I took a couple of minutes to read the operating instructions on the last mower I bought and it said to use 30w detergent oil. It went on to say that multiweight oils,10w-40w etc, would cause the engine to use oil and smoke. Take it for what it's worth, that's what it said.  

Basic rule of thumb is... "no oil pump, no multi-viscosity oil". This was prior to synthetic. The reason is that as oil pumps circulate the oil, it mixes it. Thus, broken polymer chains are spread-out in the mix.