phatboy130 said:
On a parting note, the idea that synthetics last for 20000 or so b4 needing a change doesn't sit well with me, these are the maximum recommended mileages before the oil starts to break down and lose it's protective properties, but common sense dictates that oil collects dirt and gritty particles every mile you drive, so in my humble opinion, if you leave an oil in for 20k, you are driving around with an engine full of S**t by that time!!!
Hey Phatboy,
I used to have the same philosophy as you regarding oil changes, BUT, it is worth bearing mind the advances in oil technology.
The big benefit of synthetic versus mineral based oils is that synthetic takes much, much longer to break down. This is what causes oil to lose it's essential properties of lubricating the engines moving parts.
Also, an engine in good condition should not be collecting any s**t in the oil! Certainly not grit or dirt! If the piston rings/ valve guides etc. are in bad condition then they would allow contamination to occur. But don't forget, the really nasty stuff is held at bay by the oil filter. A lot of the chemical contaminants that get into the oil will get burnt off through the breather system if the engine is allowed to run at full operating temperature. And unlike mineral based oil which breaks down over time and starts absorbing contaminants, synthetics go for much longer before any breakdowns occur.
I found this hard to swallow at first, because I was always brought up to change oil frequently. But notice how much longer modern car engines last for (150,000 miles these days is quite normal), and it's rare these days to see a car fail on engine bearings and such. This is due as much to modern oils as it is to the engine designs themselves. All engines need good lubrication however well built they are.
I went over to fully synthetic after seeing the results of a friends 1986 VW Scirocco GTX. It uses the 1.8 Golf GTi engine, except at 60,000 miles it was rebuilt and tuned by GTi engineering and taken out to 2.0 litres. This engine has now done over 300,000 miles, I kid you not, with the oil changed at 20,000 or 2 yearly intervals. It is worth bearing in mind though that this car tends to be used on long journeys at A road and motorway speeds, which is much more kind to the engine than short journeys.
It has regularly been featured in VW Driver magazine which my friend often wrote articles for.
Anyway, I switched to fully synthetic on my Uno in June 2003. It took about a year before the oil started to go dark, and even now it shows no signs of sludging like mineral based oil used to do. I've done about 15,000 miles now with this oil, and will change it (along with a new filter) next month as it has reached the two year interval.
The engine doesn't smoke, runs just as good as it did when I first got it, and consumes no more oil than it did before I switched to synthetic. Last time I looked at the camshaft it was as clean as anything with no sludge evident whatsoever. Also worth bearing in mind that I drive my little Uno hard, and it spends it's time on the motorway at 75 - 80mph as well as doing a lot of town and city driving. Not bad for a little 1.0 litre!
So I hope that it shows that you CAN leave synthetic in for much longer than mineral based oil, but of course it needs to be taken into account the kind of driving the car is subjected to. Constant town driving will need to have the oil changed sooner when compared with mainly motorway driving.
Though as you said, each to their own. I'm happy to pay extra for synthetic and change it at 15,000 miles compared with using mineral oil and changing it every 3,000 miles. That's 5 times more often than when using synthetic, and probably works out as more expensive!
I'll report in a month on the state of my oil when I drain it. Will be interesting to see if it looks as bad as mineral oil did when changed at 6,000 miles, though going by the dipstick it's still in good condition.
Chas