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johnbamfor
johnbamfor

Posted: Thu Oct 18, 2012 2:02pm

Post Subject: Engine service intervals

Our 20 year old Thorneycroft requires an oil and filter change, the Thorneycroft manual say, every 100 hours. For us that's 2 weeks out. My son's old Mondeo diesel had a service interval of 6000 miles - that was far in excess of 100 hours running - in fact he would have had to drive all 6000 miles at 60MPH. Boat engines are relatively load free, so why so frequent oil changes? Can I get away with less frequent ones, as oil and filters are increasingly expensive. She doesn't use a drop of oil between changes, has 80 psi on cold start, ticks over when hot at 40 psi; 60psi plus when at 1800 rpm.

Tony-B
Tony-B

Posted: Thu Oct 18, 2012 2:57pm

Post Subject: Engine service intervals

First of all I very much doubt that Thornycroft were still making their own engines 20 years ago. I think that they were marinising other peoples engines and I think yours is probably a BMC 1.5. Your son's Mondeo was very unlikely to spend ALL its time delivering about 4 hp (at canal speed) and at maybe 1500 rpm. It probably spent a lot of time in excess of 3000 rpm and delivering a much higher power. This means the engine and, more to the point, the oil got to well over 100c so it evaporated condensation from the piston blow by out of the oil. On a typical canal boat engine the condensation would just build up and build up. It is better nowadays with the low sulphur fuel but when that engine was built the condensation contained sulphuric acid. Add to that less "engineered" oils and you get a very conservative oil change interval. It is important that you stick with non-synthetic oils. Ideally API CC to CE but I doubt if API CF would do much harm. A SAE 20w50 oil will be fine as would a straight SAE 30 grade oil. There are few engines nowadays that have 100 hour service intervals with anything between 200 and 300 being more common. I can not override what Thornycroft says because to do so would open the magazine and myself up to litigation if anything went wrong with your engine. However on a personal note I rather tend to agree with your thoughts but do not stretch it too far. Tony Brooks

johnbamfor
johnbamfor

Posted: Sun Nov 04, 2012 1:36pm

Post Subject: Engine service intervals

Many thanks for the quick reply Tony - we've been away since I posted the enquiry and only just returned. That's really useful, and I'm not going to much if our chahge intervals extend a little, but as you say, not too much. We use Asda 10-40 non-synthetic for diesel which is a reasonable price, and have discovered a motor factors that sells the correct filter for just under £3 including VAT. Regards John

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