Good Morning JM,
I have several questions for you. What happens to a vehicle’s performance/engine when the car is subjected to a late or extended oil change? Does this affect fuel consumption for the period that is subjected to delayed oil change? And for the oil that guarantees 10,000 kilometres and 5,000 kilometres, what would be your advice/preference to motorists and the caution to take on these. Justus Maranga
To respond to your first question, it depends on how far beyond the stipulation your extension goes; and the prevailing mechanical state of your car. If the car is in good working order, you can harmlessly get away with a few extra thousand kilometres but try not to make it a habit.
“A few extra thousand kilometres” is also very relative: If you overshoot your service interval by 20,000km, then you only have yourself to blame when your engine digests itself or tries to commit gunk-based seppuku. I repeat: try and stick to the programme. It is for your own good.
It need not be said that older, higher mileage engines are more intolerant of unfaithfulness to the servicing timetable. This is especially pertinent to vehicles operating in extreme conditions; the sort where people working there have to be paid a hardship allowance. If you operate in dusty conditions, ford water often or even drive in normal places but the engine is always under a lot of load, yea, you should stick to the schedule or pay the price.
To your second question, I would have thought not, but this was made very apparent and very clear during the final two months of 2018.
I mentioned earlier that a W210 Mercedes-Benz E Klasse joined the garage in 2.3 litre, M111-powered, 4-cylinder form. Now, shortly after acquiring it, I subjected it to an extended road trip up the walls of the Rift Valley and I must say the fuel consumption was not impressive at all.
The seller sternly reminded me that he had specifically said to service the car as the first order of business. The car was duly serviced and subjected to yet another extended road trip, this time past the walls of the Rift Valley and lo and behold!
Same driver, same driving style, same roads, broadly similar conditions but this time, the car just wouldn’t drink. I know theories about engine compression come up when discussing oil but the Benz doesn’t have that many kilometres under its belt and I did not think the difference would be that extreme.
I have pushed both El Turbo and the Mazda lago beyond recommended service intervals (but not by far) with no discernible flagging in performance or economy, but in the Benz, it really was shocking.
Finally, the advice/preference/caution is fairly obvious but it may bear repeating just to be sure: stick to recommended service intervals, don’t create your own.
Read The [expletive] Manual and find out the kind of oil the manufacturer engineered your motor for. Don’t do the equivalent of smearing Vaseline on a Formula 1 crankshaft and expect that engine to see tomorrow.