Oil issues

[kb280dtza]

My old Isuzu KB280 (South Africa) is at 470k kms on a second engine, a used Jap unit. At this age I do servicing myself. Previous service I used a new Shell Helix (15w40) oil for diesel engines, of which in the fine print, which I read after topping up my engine is for engines with indirect injection. I immediately felt that the engine was noticeable rattling (tappet noise) and I even went to adjust the valve clearance with no difference noted. Last week I did another service after 7500 km and used my old oil a Castrol GTX Diesel (15w40) and the engine has gone quiet again. How is that? Do oils really differ so much? I alwsys thought it was just marketing crap.

[geeves]

Indirect injection does result in more stuff getting into the oil so a higher detergent level is required. Your helix I suspect is a partial synthetic oil so will be thinner when cold which does make for better lubrication when cold and hot but doesnt insulate various noises as well as the GTX. Both oils are fine but I would still use the Helix unless it costs lots more than the GTX.
7500 km is a long service interval. I would only consider this ok if you do mainly long trips and I wouldnt trust the GTX at that interval. All the rest of us change oil at 5000km

[kb280dtza]

Thanks for the explanation. As for service intervals - I have closely followed the recent history of Isuzu in South Africa - General Motors South Africa. They have been constantly adjusting the oil change intervals in response to what they say is due to improvement in the quality of our diesel fuel which I am told was once very dirty. They changed them from 5000 to 7500 km in the old model and when the DMAX arrived in 2004 it was at 10 000 km and now its at 15000 km. The latter caused an uproar amongst owners with cars under Maintanance Plan as the number of services due by GM was reduced before the 100 000 km cut off.

[kb280dtza]

Thanks for the advice I will do the 5000 km intervals as written on the bonnet of my truck.

[geeves]

3 things have improved the service interval Some you can take advantage of
1 fuel New fuels have less sulphur so less acid. This is why the old interval had 6 months as well as the mileage.
2 oil quality has improved with synthetic blends and better detergents. Your old engine specified CD oil now the lowest you can get is CH
3 engine design. By design common rail engines are cleaner so less load on the oil
First 2 you can take into account if you want to run a longer service Personaly I would stick to 5000. Oil is quite cheap insurance