4-stroke lawnmower engine oil

veryangryman

Bought a new lawnmower other day (first to own so forgive my novicity..)

Looking in various places for this last few days. Nearly all shops have 2-stroke, but none specifically say 4-stroke. Is it that they go by a different name, or can you recommend a place that does sell them?

CJhaughey

The two oils are very different.
2 stroke oil is designed to be mixed with the petrol and lubricates the engine as part of the combustion process.
4 stroke oil is inside the engine to lubricate the internals of the engine and is changed every XX amount of hours or once a season(if you are lucky).
Your new mower will already have oil in it, there should be a dipstick on the engine somewhere that you unscrew and use to check the level.
There should be no need to add any 4 stroke oil to the engine under normal conditions, the engine should not use any oil.
If you want to buy some to do an oil change B&S engines use straight 30w oil, others like Kawasaki and Honda use 10w-30 or 10w-40 oil.

walus

Use a full synthetic 5w30. Not only it is much better oil for the 4 stroke engine, it also comes out cheaper and is widely available in motor factors. See here: http://blog.briggsandstratton.com/synthetic-vs-conventional-oil-what-do-i-use-in-my-small-4-cycle-engine/.

CJhaughey

I doubt you will see any benefits from using 5w-30 fully synthetic over straight SAE30 in a Briggs engine,its overkill on these old engine designs.
You still have the same service intervals and its more expensive.
5 litres of 30w oil is around 20 euro, I don't think I have ever seen any fully synthetic 5w-30 for anywhere near that price.
It's your money though, spend it how you wish.

Mech1

CJhaughey wrote: »

The two oils are very different.
2 stroke oil is designed to be mixed with the petrol and lubricates the engine as part of the combustion process.
4 stroke oil is inside the engine to lubricate the internals of the engine and is changed every XX amount of hours or once a season(if you are lucky).
Your new mower will already have oil in it, there should be a dipstick on the engine somewhere that you unscrew and use to check the level.
There should be no need to add any 4 stroke oil to the engine under normal conditions, the engine should not use any oil.
If you want to buy some to do an oil change B&S engines use straight 30w oil, others like Kawasaki and Honda use 10w-30 or 10w-40 oil.

Some lawn mowers ship without oil, http://www.homedepot.com/catalog/pdfImages/ac/ac5ade48-1e59-4368-966a-f70964130c8a.pdf

walus

CJhaughey wrote: »

I doubt you will see any benefits from using 5w-30 fully synthetic over straight SAE30 in a Briggs engine,its overkill on these old engine designs.
You still have the same service intervals and its more expensive.
5 litres of 30w oil is around 20 euro, I don't think I have ever seen any fully synthetic 5w-30 for anywhere near that price.
It's your money though, spend it how you wish.

5w30 full synthetic is superior in any way to a straight dino SAE30. Experience eye/ear will spot the difference relatively easily. The engine would benefit from it regardless. It lubricates much better at the startup and shortly afterwards. On top of that it leaves the engine in much cleaner condition and it is available in any car parts shop.
I was comparing prices for small bottle oils and SAE30 0.6L is about 6 euros, while 1L 5w30 can be gotten for 8-10 euros depending on place and make of oil. Very good quality 5w30 in 5L cans can be gotten for as little as 25 euros.

CJhaughey

I can't agree that using full synthetic 5w30 oil in a B&S is a good idea.
The tolerances are so loose and the general build is so sloppy that it won't make a blind bit of difference at the end of the day.
Just changing the oil once a year is enough to keep them running fine.
Its like putting expensive synthetic oil in an old car, a waste of time and money using it in something that was never designed to use it.
I have rebuilt enough engines of all kinds to know that many engines don't need fully synthetic oil, not only that its actually counterproductive in that a lighter multigrade oil like 5w can burn off a lot faster than a thicker oil like 30w.

But its your money and if you think using fully synthetic 5w30 in a Briggs will make it last longer then don't let me stop you using it.

walus

CJhaughey wrote: »

I can't agree that using full synthetic 5w30 oil in a B&S is a good idea.
The tolerances are so loose and the general build is so sloppy that it won't make a blind bit of difference at the end of the day.
Just changing the oil once a year is enough to keep them running fine.
Its like putting expensive synthetic oil in an old car, a waste of time and money using it in something that was never designed to use it.
I have rebuilt enough engines of all kinds to know that many engines don't need fully synthetic oil, not only that its actually counterproductive in that a lighter multigrade oil like 5w can burn off a lot faster than a thicker oil like 30w.

But its your money and if you think using fully synthetic 5w30 in a Briggs will make it last longer then don't let me stop you using it.

Sure that a straight SAE30 is enough to keep the engine going. The 5w30 full synthetic is much better though. I did a simple comparison this weekend and mow the lawn at the back with the B&S SAE30 oil that the mower came with (oil had maybe 3.5 hours of total usage). For the front yard I changed the oil to 5w30 full synthetic (Granville - so far from top of the range oil). The difference was massive - the engine produced noticeably less vibration and substantially less noise. If that is the effect 5w30 has over straight dino 30 then surely it has to be doing some good to the engine. I do not see a point in using SAE30 when you can have far superior oil at essentially same price. I'm not going to try convert anyone to the obvious fact - your mower your choice how you run and service it. I know what I'll be doing with mine.

CJhaughey

walus wrote: »

Sure that a straight SAE30 is enough to keep the engine going. The 5w30 full synthetic is much better though. I did a simple comparison this weekend and mow the lawn at the back with the B&S SAE30 oil that the mower came with (oil had maybe 3.5 hours of total usage). For the front yard I changed the oil to 5w30 full synthetic (Granville - so far from top of the range oil). The difference was massive - the engine produced noticeably less vibration and substantially less noise. If that is the effect 5w30 has over straight dino 30 then surely it has to be doing some good to the engine. I do not see a point in using SAE30 when you can have far superior oil at essentially same price. I'm not going to try convert anyone to the obvious fact - your mower your choice how you run and service it. I know what I'll be doing with mine.

Firstly SAE30 oil is not always mineral oil,there are good quality semi and synthetic staright weight oils as well.

Multigrade oil is not inherently superior to straight weight oil, it depends very much on the intended usage and operating conditions.
Air cooled Aircraft engines commonly use monograde oil usually SAE50w because they are stable in use and do not suffer from the negative effects of multigrade oils.

Multigrade oils are primarily designed to provide better lubrication at startup in cold conditions than straight weight oils. This is because a car engine is watercooled and in winter temperatures below zero are common, the winter rating is denoted by the (w) after the first weight.
The second figure is the weight of the oil at 100°c
In order to get the oil to resist thickening too much at high temperatures they add viscosity improvers, these are additives and as with all additives they work until they are used up.
At higher temperatures straight weight oils resist thinning much better, that is why aircooled plane engines use straight weight oil.
A lawnmower is aircooled and operates typically within a fairly narrow range of temperatures , usually between 15 and 30°c ambient.
The oil warms very quickly in a lawnmower usually around 1-2mins will see it at full temperature, cold running performance is not crucial to these engines and most excluding Kawasaki engines are simply splash fed lube systems.
Heat and pressure break down the additives and as the viscosity improvers break down the oil thins, this can result in the oil reverting back to the base oil viscosity which in 5w30 is 5w oil, this is obviously not ideal for rod bearings and premature wear can be expected if the oil is not changed on a regular basis, which in my experience most lawnmowers suffer from.

If cold weather performance was critical such as below zero start ups then yes a multigrade oil may offer significant benefits but for a lawnmower used in Ireland in the summer, it is my contention that a straight 30 weight oil is actually better in the long run than a cheap synthetic that may cause more issues than it purports to solve if not changed regularly.

If you want to compare like with like then use a decent SAE30 oil alongside the 5w30 not just the delivery oil which is generally the cheapest stuff they can fill the engine with at the factory in Chonqing.

walus

I understand what you are saying CJhaughey. Some applications do call exclusively for a monograde type of oil but in some other options are possible. In my opinion however a car engine has a much tougher life than the one mounted on a lawn mower and surely if it is good to last 10k kilometres in a car it is more than adequate to stay in grade for a season in a lawn mower. The comparison that I did was against a B&S branded SAE 30 oil - so one recommended very much by the engine makers themselves. In the past multigrade oils were very prone to shearing. Nowadays they stay in grade even though are exposed to very harsh conditions in turbocharged petrol and diesel engines and I would have no issues using them over a straight SAE 30 as even B&S say themselves it is a better oil for their engines.

mikeecho

so what type of oil should a mower typically take ?


??W??

Semi Syn/ Fully Syn/ Mineral ?

CJhaughey

mikeecho wrote: »

so what type of oil should a mower typically take ?
Semi Syn/ Fully Syn/ Mineral ?

It depends on which engine you have on your mower.

Walus contends that a fully synthetic 5w-30 car oil is a better oil for his Briggs.


In my opinion a good quality Mineral 30w oil is fine for Briggs engines, for Honda or Kawasaki engines 10w-30 is called for and I would use a good quality semi-synthetic oil.
In Ireland cold running performance is not critical so a light W rated oil like 5w-X0 is not necessary, we don't have snowblowers.


What ever oil you do choose to run make sure you change it at the end of the cutting season, as the mower is laid up old oil becomes acidic from the
combustion waste not good to have in over the winter.
New Airfilter, the deck cleaned and you should be good for many years of cutting.
Most engines I have rebuilt have been killed by lack of maintenance not wear.
In the few that did wear, it was many many hours of cutting that wore the rings out, and even then it was a simple rebuild.

walus

I do think that full synthetic 5w30 is best for B&S engines. It is not only my observation and opinion but also something that B&S say themselves: "A synthetic oil SAE 5W-30 is the best for very cold temperatures of -20 to as high as 120° F (-30 to 40° C) providing the best protection at all temperatures as well as improved starting with less oil consumption". It is available pretty much in every car parts store which is also a good thing. It is important however to change the oil regularly - it is a bit like with brushing your teeth - you do not do it less often even just because you use top of the range tooth paste. Stick to recommended service intervals and you will not have to worry about the condition of the engine in your mower.