All engine faults/repairs/maintenance Oils recommended
General
This page still under construction by CovKid.
Engine oil has perhaps been the most talked about subject on 80/90, frequently the most neglected and often the least understood so we've decided to create a more extended WIKI section for engine oil with answers to the most common questions. This page is for stock engines found in the T25 range and the recommended grades for each. It does not recommend 'makes' of oil as that is not actually of much relevance - nor should you pester other 80/90 members to find out what they use. Everything you need to know is here - make your own choice. If you just need a quick answer without too much brainstorming, skip down to the Petrol or Diesel sections and the suggested grades are there!
For everyone else, reading through should give you a greater appreciation of the role of your oil, what may or may not work for your engine, and whether paying more, delivers more. It doesn't aim to be a definitive guide but has additional links for those that want to explore beyond the content provided here. Alternative engines, Subarus, V12's whatever, fall outside the remit of this section. In such instances you should consult the manufacturers recommendations for that particular engine. 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.
Oil And What It Does
Engine oil actually serves a few purposes beyond lubrication. Oil also cleans, inhibits corrosion, seals and cools an engine. Oil has to work fairly hard and in varying temperatures, particularly with the aircooled.
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 even 80/90 members disagree, 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 mystery thingy". Personally, I rarely pay more than £10 for five litres (2011 prices). To my mind spending £40 on oil is akin to those who buy premium unleaded fuel in the belief that they are somehow spoiling their engine. Oil manufacturers notoriously play on this kind of guilt so don't be guided exclusively by slick marketing. You are not driving a Ferrari.
However, one thing we do all agree on is no matter what oil you use - change it regularly. Regular oil changes extend the life of your engine and keeping the oil clean and topped up matters 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. Engine oil generally has a shelf life of around 3 years.
Many modern oils (read the label) are formulated to work in both petrol or diesel and a 'close enough' oil type (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.
How Often Should I Change My Oil?
Well, it depends. The flat four aircooled engine needed changing (ideally) every 3000 miles but as well as running at a higher temperature compared to the watercooled, it also lacked the luxury of an oil filter. The oil change frequency was therefore extended slightly on later engines. I drive a watercooled 1.9DG petrol and cover around 12k miles a year, changing the oil twice a year. However, if for any reason it looks black or somewhat thin, I may bring the oil change forward. The recommended minimum for oil changes is every 6,000 miles or six months - whichever comes sooner.
I once had a long conversation with a biker who (because of his job) had an unlimited supply of oil. He changed his oil EVERY week whether needed or not and said it had the appearance and performance of a brand new engine even after 100,000 miles. I have no reason to disbelieve him but neither can I uphold his claim. I only mention it because it illustrates how important regular changes are to the life of an engine.
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 cheaper 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 to 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 consider it 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. We're not ruling out synthetic and you may wish to go that route but if your engine is a bit of an 'oiler' the problem may well be made worse with synthetic. It is possible to find grades as wide as 5W50 in synthetics. The price is generally higher for synthetics too.
Do NOT mix mineral and synthetic as it could seriously reduce the capacity of the oil to do its job, and at worst render it useless.
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)
Oil Types And Other Thoughts
Increasingly modern oils seem to come in wider ranges but 15W/40 is a fairly common spec and readily available. 20W50 (at a pinch) would also be fine but perhaps climate change with sometimes excessively cold winters may preclude 20W50. I do know of owners that use 20W50 in the Summer and 15W40 in the winters and other combinations. Likewise, a diesel oil (which tends to have more detergents) could also be used - more so these days as the gap between diesel engine oil and petrol narrows. 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 seem to prefer or opt for 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, or rarely, premium fandango brands disguised in a budget container. By the same token, it does not follow that spending £40 on a can of oil promising the earth 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 even if it makes the owner feel better. 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, particularly if the engine has done many miles. 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.
Petrols
1.9, 2.1, 2.0 etc:
The specified oil is SAE 15W/40 for petrol engines - multigrade. You won't go far wrong sticking to that. 15W50 would also be a good choice - particularly for aircooled engines which can run hotter. Change every six months or 6,000 miles - whichever comes sooner.
One aircooled owner recommended 20W50 on the basis that 15W40 is more likely to seep past gaskets but we have no scientific evidence to back this one up at all and any seepage could simply be down to the quality/brand of the oil rather than grade and indeed symptoms of an old engine. I've only added this as the question came up in a thread.
Diesels
15w40 or 10w40, and an oil suited for Diesel engines. As noted earlier in this page, many modern oils are suitable for either petrol or diesel (read the label) but most 80/90 members feel that its best to find an oil that is primarily for diesel and preferably for Turbo diesel.
Quantities (as we note them):
1z TDI - 4.5 litres + the filter
Good links
http://www.carbibles.com/engineoil_bible.html
Oil filters and recommendations
