Oils Ain't Oils

Just buy the correct specification oil for your engine.

Warrie.
The common beliefs about oils is alarming.
I cannot see why you can't use a 15W40 in a Prado. The mechanicals are made to the same clearance specs as engines 20 years ago so the oil won't know the difference. If you understand what 5W40 or 15 W40 means is ONLY one thing. AT startup a 5W40 will flow through the engine a little quicker, and flowing oil pressure will be there in a couple of seconds, where the 15W may be 1/2 a second behind. The oil pump is a positive displacement device. It has to deliver when turning. It can't build up pressure in one place before another, so all the engine is covered. However, although thinner/less viscosity at startup, a 5w40 is the same viscosity as a 15W40 WHEN IT IS HOT, so nearly all the time your engine ever runs it is running on what viscosity a 40W oil would provide, ie. no discernable difference. A heavy duty engine, what ever that is, has much the same clearances as a smaller engine. I used to rebuild them.
I have had a Turbo Landcruiser and a Dmax , total of 35years of personal diesel engine use and all ran on 15W40. Only in very very cold climates where a bit thinner at startup may be an advantage is a 5W40 of any use.
ALL engines, diesel or petrol where I used to work ran on 15W40 Mobil Delvac Diesel oil. NO failures.

5W viscosity when cold warms up, and then the 40W aspect is what the engine runs on when hot. The oil although rated at 40W and now HOT is actually thinner than COLD 5W oil is. It is called Multi Grade.
In other words, at some time as it warms, both 5W40 and 15W40 will pass through a temp point where the oil IS the same thickness anyway and it IS the 40W which the engine relies on during it's operating time and NOT the 5W feature.
If using 5W40 the engine may use more oil than it's normal usage as thinner oil will mist in sump with blowby gas and pass the rings easier and be burnt off in the cylinders or ingested more readily VIA the EGR system.
Are you thinking it is too thick somehow, posing the question or is someone putting ideas into your head to create doubt?
PS. WHY is CASTROL cheaper?
Cheers

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Hi Warrie,

It is not advisable to mix differing oils. The following is an extract from Penrite Oils.....

"Mixing different types and viscosities of oils changes the original chemistry balance of the oil and may result in an unsuitable product for certain types of applications. So although the base oils will mix quite readily, the additive packs used in them are designed for particular applications and a combination of these is an unknown concoction in terms of performance and compatibility. In certain circumstances, putting the wrong oil into an engine can cause extensive damage to the engine or components associated with it. It is always best to use the same type, viscosity and manufacturer specification when topping up your engine oil."

G/Day Warrie,

I think RMD has covered it pretty well, I have used 15W- 40 for years in small and large engines without troubles, some do seem to have better ring sealing agents than others, less blow by, but thats just a personal opinion, my choice these days is Penrite 15w-40. ..My worry now is the wifes late model Honda talk about thin oils!, but thats the dealers problem, for the next few years, there the one carrying the warranty and the extended one.

Cheers Axle.

Hi Warrie,

There are a lot of people out there that buy the cheapest engine oil, and then rave about how good it is. After 35 years in the Oil Industry, one thing I can tell you, is Oils ain’t Oils. The best engine oils take years of research and development, including “real world” testing to get the standard of protection that they claim. Buying a “no name” engine oil, or one with a “distributor” name, is not necessarily going to give you the engine protection that may be required.

All of the major oil companies manufacture to the highest standards, that is why they have been in business for as long as they have. So whether you buy Castrol, Mobil, Penrite, Shell etc. rest assured in the knowledge that there are years of research and development behind their product.

Both RMD and Allan have explained the difference between the various grades and how they work quite well. Look up what grade of engine oil is recommended by the engine manufacturer, and stick to that.

As an aside, Toyota have engine oil under their own brand name. It is manufactured by one of the major oil companies to specifications set down by Toyota. I can tell you that it closely mimics Mobil 1, and there is a good reason for that.

Macca.

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One solution is to never change the oil at all.......

I once knew a bloke who was a genius at buying a reasonable car dirt cheap. He made sure it had good tyres and a bit of rego. Never changed the oil and did no maintenance whatsoever.
Kept it for maybe a year or until the tyres were bald, then sold it for as much as he paid for it.
Always had wheels under him and his only cost was fuel.

Like I say.... a genius!!!