How Often to change the Oil

Not sure about M numbers. It's certainly a 12 valve and has a timing belt. Car is '87.

I can only say that you have little or no idea of how lubrication works.

Huw

I said all but obsolete, which means not quite.

Huw

So it's just a faith rather than based on experience? When cars had 3000 mile oil change intervals did you do it at 1500?

Dave Plowman (News) ( snipped-for-privacy@davenoise.co.uk) gurgled happily, sounding much like they were saying :

I've got one with a 1500 mile oil change interval...

No filter at all. Just a strainer on the pickup in the sump.

Could certainly leave it longer. It has 20,000 mile recommended oil change intervals. You just said so.

Huw

I've got a very good idea how lubrication works.

Why do you think I don't?

Since I have to spell it out, if you *did* know you would not say that "you cannot change oil too often" because you would know that there was no advantage to changing oil before an actual oil change was *needed*. That is, put simply, before the particle size and quantity of contaminants saturated the film such as accelerated wear took place or overwhelmed the dispersant capacity. Also before the viscosity of the oil changed unduly either to become too thin or too thick, both of which are possible.

How do you know when this is the case? At its simplest you follow the car manufacturers recommended service schedule which provides a decent allowance for variation in vehicle use.

Running an engine for 50% or more over the service schedule may have consequences [or it might not depending on all kinds of things] but servicing according to the schedule using recommended materials seldom has any adverse consequences. For severe use then shorten the schedule by 25% or use a better standard of oil [if you know one when it bites you] but to say what you say is just plain silly and it is unnecessary.

Huw

How do manufacturers know what is right? They've been proven wrong many times in the past.

Really? Anyone want to tell Huw how many cars have had cambelt change intervals reduced because the mftrs were over optimistic?

Nope, when they had 6000 I changed it at 3000, this was mainly town driving.

I'm not quite sure what you are getting at here? Am I offending you in some way?

Name them. About five examples of car engine types that suffer common lubrication failures or undue wear at recommended intervals will do.

I can think of three or four, some due to factors other than the belt itself failing as the primary failure. Statistics are examined and schedules altered as a conseqence. This is an indication of the manufacturer's service department systems of monitoring customers cars working well. If there is any significant oil related issue then the same would happen to oil change intervals. They continue to increase on average.

In the case of most extended intervals of 15000 miles and above the oil is actually monitored for condition and signs of breakdown dynamically. If certain conditions are breached then the oil service warning light will warn the driver to change the oil. It works and works well.

Huw

That's an interesting one

In the late 60's I had a Honda CB250 motorbike - which had a centrifugal oil filter bolted to the end of the crankshaft, that had to be carefully cleaned out at every oil change.

Oil change interval on this machine was 1,000 (that's right, one thousand!) miles.

I suspect this was because of the high-revving nature of the engine (power came in at 7,500 rpm, redline was at 10,500), it was air-cooled (does that make a difference?), and the oil served the gearbox as well - plus oil technology in the late 60's isn't what it is now.

Lots I suspect.

Mid - late 80's Orion/Escort OHC engines had a cambelt change interval of

Colleague took car in for a check-up, and while there a car was towed in with a blown engine - cambelt let go at 27,000. Colleagues car had done -

Relative running a fleet had similar experience with all similar cars - put cambelt changes into the fleets schedule for 25,000 and had no more blowups.

I always assume the mfctr interval is too long - and reduce it by 30 - 50% for most things.

Oh - the spark plug change interval on my current car is supposedly 40k - so while it was under warranty I simply left them in place. When it strted misfiring I took it in, the plugs were replaced under warranty - at 39,000 miles would you believe! (Now its not under warranty it will be done annually at about 20k or so.)

Mind you, even cambelts these days last better than the valve gear on some of the older puhsrod engines - the austin/morris "b" series for example .....

I think its just that it takes a long time - 40,000 - 50,000 miles - and you don't really notice it unless you keep records of fuel consumption etc. - but a huge number of people simply don't keep cars that long, and they never notice at all.

I think the computer does things a little more dynamically in some way than the fixed intervals you find printed in the handbook - and I suspect that under certian types of driving (maybe stop/start, town driving etc) it may tell you to change the oil at a much shorter interval than the usual "20,000 miles or 12 months" schedule. If I had a similar device on my car then I would follow it's advice.

Actually in the 60's some cars still had oil change services of 300 miles.

Even now a motorbike might only do 1000 miles on an oil change if it's a high performance model, and/or ridden 'enthusiastically'.

Yes, all of that makes a difference for sure, the higher revving nature causes greater sheer stresses, and the air cooling often results in higher operating temperatures. The gearbox itself causes very little contamination, other than particles of metal from missed gear changes.

Even now I change the oil on my FJ1200 every 2500 miles, despite the manufacturers recommendation of 4000 miles.

Observation of the condition of the oil shows that the oil really does need changing more frequently.

Having said that if you RTFM, nearly all manufacturers state that oil should be changed at shorter intervals under harsher conditions. This might be a variety of things, like stop start driving, driving on congested roads frequently, or driving under high stress conditions frequently.

Not many people believe they actually use their car under harsh conditions - 'I only use it to pop to the shops a couple of times a week, but I do take it on a long run once or twice a year', is quite normal. They often only appear for service once every 18 months to two years. Of course, the oil is thick, and the brakes seized.

OK, I can certainly name a couple.

Alfa Romeo Ts engines for one. I saw these being constantly replaced at low mileages, even with normal servicing.

Ford OHV engines, actually wear out at 30k.

I've also heard of a Citroen C5 failing (family member, regularly serviced, and only just out of warranty - Citroen did not assist).

The VW engines (also used by Seat and Skoda) also fail prematurely too - this is a big known problem.

Actually I agree there, most premature cambelt failures on modern cars are caused by the crap quality tensioners and water pumps that are used now.

Some examples?

Not me, but recommending early oil change intervals is just wrong and a waste of money. Unless you have some proof it extends engine life. And common sense says it doesn't. In the days of 3000 mile oil changes engines might only last as long as a set of tyres before overhaul was needed. Certainly more than one overhaul in the life of the car. These days engines generally outlast the car - unless suffering a failure unconnected with oil changes.