All engine faults/repairs/maintenance Oils recommended

General

This page still under construction.

Engine oil serves a few purposes including lubrication, cleaning, inhibiting corrosion, sealing and cooling. It also has to work fairly hard and in varying temperatures. This new page (in progress) shows the recommended oils for stock engines found in the T25 range and explains in simple terms, the numbers attached to oils. Alternative engines, Subarus, V12's whatever, fall outside the remit of this section and you should consult the manufacturers recommended lube chart for that particular engine, otherwise read on....

Firstly there is no 'right' or even 'perfect' oil but the basic recommendations below are certainly a good starting point. Engine oil is always being developed and not everyone here agrees, some preferring monograde (though why escapes me), some using cheap or expensive multigrade (multigrade being versatile and able to cope with a wide range of conditions), and even "Fantabidosa premium brand with added thingy" but one thing we do all agree on is no matter what oil you use - change it regularly. Regular oil changes and keeping the oil topped up matter far more than how much you actually spend on it. The VW engine isn't doing the high revolutions of most modern performance-orientated cars so will run quite happily on a budget brand (within reason) providing you change it regularly.

Many modern oils (read the label) are formulated to work in both petrol or diesel and some oil (even if not the ideal choice) is better than no oil at all. Listed below are VW recommendations followed by opinions and ideas put forward by various 80/90 club members over the years. Draw from it what you will. Additional links are provided for anyone who has time to kill and for reasons I have no wish to know, want to explore the world of 'oil' in more depth.

Numbers - What Do They Mean?

Oil grades are numbered. Heres a brief explanation of what it all means.

Firstly, old-fashioned monograde (which is what it is - one grade) can thin at higher temperatures and generally, does not offer anywhere near the protection of most modern multigrade oils, designed as they are to perform at a larger operating temperature range. Even some of the cheapest multigrade is at least comparable with that recommended by VW in 1980-1990 and certainly before that. There are purists, particularly amongst bug owners who only use monograde, but these days, the advantages afforded by a good multigrade would seem to far outweigh any puritanical view that monograde is the right, or even only oil one should use. In 1938 perhaps (the birth year of the T25's ancestor), but even the humble beetle now has to keep up with the stop-start fury of modern traffic. Besides, it makes more sense use an oil that can perform reliably and consistently throughout the year, from a freezing cold start to a baking hot day at high speed. Clearly there is a marked difference in temperature between starting an engine on a cold winters morning and an hour later hammering down the MI.

This difference in operating temperatures of engines, spawned the development of multigrade oils and removed the high demand for various specific grades, resulting in a largely 'one size fits all' approach to engine oils. Even the gap between diesel and petrol engine oils has narrowed with many oils suitable for either. Basically, multigrade engine oil numbers denote the cold and hot viscosity either side of the 'W' so 15W40 oil would perform like a 15 rated oil from cold and like a 40 when hot.

Following from that, a 10W40 would perform like a 10 rated oil from cold but some owners maintain that 10 is too thin for the VW engine and more likely to work its way past pistons and burnt although in exceedingly low temperatures more familiar to Eskimos, a low rating of 10 would be advantageous if you need to be up and about to trap seals. You get the picture.

Mineral oil is commonly used in T25s. So why not synthetic? Well some do use synthetic oil, which generally has better heat transfer qualities and theoretically works well in aircooled engines which can see elevated head temperatures, but only if you have an oil filtration system (similar to those on watercooled engines instead of a simple oil strainer), otherwise the oil will become contaminated much more quickly and the additional cost possibly not justified. The other downside, and worth noting before you rush out and buy synthetic oil, is that it will find the tiniest leak and you could end up with oil spots all over your driveway. It is possible to find grades as wide as 5W50 in synthetics.

SAE denotes that the oil is graded as per that specified by the Society of Automotive Engineers (a benchmark basically) and API denotes the quality of the oil, confirming that it meets certain specifications. More on API can be found in the great Engine Oil Bible (see footer links)

Petrols

The specified oil is SAE 15W/40 for petrol engines - multigrade mineral oil (see notes above on synthetic oils). Increasingly modern oils seem to come in wider ranges but this is a fairly common spec and readily available. 20W50 would also be fine but perhaps climate change with sometimes excessively cold winters may preclude it. I do know of owners that use 20W50 in the Summer and 15W40 in the winters. Likewise, a diesel oil (which tends to have more detergents) could also be used. I ran a bug on Shell Rimula diesel oil throughout its entire life with no ill effects. In any event, if that was all the garage had in stock on Sunday morning, I wouldn't turn my nose up but certainly the recommended grade is 15W40 multigrade and the vast majority of T25 owners use mineral rather than synthetic.

You can find good quality oil that meets and more often than not, exceeds VW T25 spec from some supermarket outlets these days and often, petrol forecourts have limited offers on engine oil. As has been pointed out by other 80/90 members, cheap oils can be absolutely fine but oil is an expensive commodity and they are not premium fandango brands disguised in a budget container. By the same token, it does not follow that spending £40 on a can of oil is going to be far superior in a T25 than the can you saw priced at £10 either. The VW flat four is a fairly low-revving engine and an oil better suited to a high-revving race engine is probably wasted on the VW engine. It would however be wise to steer clear of containers that provide very little information at all, but certainly don't rule out an oil simply because it is cheap or assume that the more it costs, the longer your engine will last or the faster it will go. Read the label, and if it seems reasonably good, go by your instincts.

As mentioned earlier, the concensus on 80/90 is that good old fashioned mineral oil is the best choice. Mineral oils are, as the name implies, based on oil extracted from beneath our feet, and refined. Synthetic oil (you could see it as a 'designer' oil if you like) is manufactured from various chemicals, although by and large, most of the ingredients do in fact derive from mineral based oil products. The molecular particles are much more even with synthetic oil which is why (technically) it has better heat transfer properties but as noted above, some have experienced minor oil leaks on both water and aircooled VW engines with synthetic oil, only cured by going back to mineral. The other type is semi-synthetic - a mix of the two. Further links are provided in the footer if you wish to explore synthetic and semi-synthetic oils in more depth.

Good links

http://www.carbibles.com/engineoil_bible.html

Oil Changes - Petrol Engine

Oil filters and recommendations