Really Bad Engine Sludge...

[jcboy]

1) engine flush is not good, it flushes even the oil films on the pistons/rings.

2) use a multigrade multipurpose oil (for diesel and gas engines), then use it for 1000km (~600 mi) then drain it and use a good oil like mobil 1.

3) never use lower than xxW-40 oil, since your country is a bit warm/hot, oil will thin out a lot if its like xxW-30 or lower (don't worry about the xx since that is cold weather rating). if your oil thins out a lot, oil degredation will likely happen more/faster.

4) toyota nz and zz engines were/are rumored to be prone to sludging, don't use conventional oils for more than 5000km (~3000mi) and FULLY synthetics for more than 10k km (~6000mi).

i would assume this is mostly city driving and since sludging is partly caused by pollution as well as long oil change intervals. if it is dusty where you drive most of the time, be sure to change the air filter every 4th oil change.

HTH :)