Choosing the correct spec oil for the Hilux Surf.
Article: Deucer. (RandalG)

Think it's time to bring some clarity to the issue of engine oils and what's good, better or best. It's not about the brand. The definitive test of a quality oil is the minimum specifications the oil is manufactured to achieve and whether or not those specifications are relevant to the engine you want to use the oil in. So here goes my General Rule of Thumb for the 2LTE engine in the Hilux Surf (same may apply for 1KZTE engine in Hilux Surf).

Preferred Oil for 2LTE Engine:

The Rule:
Assuming your engine is in good working condition; an oil that meets and does not overly exceed the following minimum performance specifications and standards is the best oil for your engine according to the manufacturers recommendations (which by the way is):

Manufacturers minimum recommendation (1990 2LTE operating in Japanese service conditions):
- Winter: 10W-30 diesel engine oil with API rating of CD.
- Summer: 10W-40 diesel engine oil with API rating of CD.
(API: American Petroleum Institute)

But our vehicles operate in Australian conditions and better oils have been developed over the years.... Particularly oils for Japanese manufactured diesels which have specific lubrication requirements that differ from European and/or American manufactured diesels. So my interpretation of the theoretical best oil for protection of the 2LTE engine (manufactured between 1990 to 1994) is an oil that meets and does not exceed the following minimum requirements:

- 10W-40 to 15W-40 all seasons; mineral or synthetic
Why a heavier weight (thicker) oil than the Japanese recommendation? Because Australian temperatures are generally warmer than in Japan. There are exceptions offcourse.

- Compliant with API CF or CF-4 specifications.
Oils built to a higher specification than CF-4 (ie: CH-4, CG-4 and CI-4) may have too strong an additive package for the 2LTE (and possibly 1KZTE) engines manufactured between 1990 and 1994. A risk of using this oil is bore glazing for engines that do not see severe duty.
An example of an engine working under severe duty service conditions is a semi-trailer travelling from Brisbane to Perth fully loaded, or a Hilux Surf that does nothing but sit and idle in traffic all day. Service conditions between those two extremes generally represent normal duty service conditions.

- Compliant with JASO DH-1 specifications
Provides improved valve train protection for Japanese manufactured diesels, amongst other things.
(JASO: Japanese Automotive Standards Organisation).

The Exceptions:
(1) A heavier weight oil may suit older and/or well worn engines to minimise oil use. I can't tell you what, if any impact this has on other internal engine components (ie: seals & components with tight tolerances). Generally speaking, I think it's fair to assume that if your engine's using oil, something needs fixing.... be it the oil or the engine. But a heavier weight oil may be an effective stop gap.

(2) In some circumstances, a lighter weight oil may also be suitable (eg: Mobil 1 5W-50, SJ/CF). However, you’ll likely notice oil consumption sooner rather than later with the lighter oils (speaking from experience here). A heavier weight oil and/or properly specified oil will correct that if consumption is purely related to the weight of the oil.

(3) An oil that meets all the above requirements should be the BEST oil for your 2LTE engine...... BUT It's not an ABSOLUTE NECESSITY to have an oil that meets ALL those requirements. Simply using a good quality, SJ/CF rated petrol/diesel engine oil with oil changes every 5,000km and oil filter changes every 10,000km will adequately protect your engine under normal duty service conditions (according to manufacturers recommendations). For severe duty service conditions, oil changes should be every 3,000 and oil filter every 6,000km as per manufacturers recommendations.

(4) There are a number of diesel specific mineral oils on the market that are designed to deliver extra engine protection, cleanliness and facilitate extended oil change intervals. It’s claimed that some synthetic oils can also deliver similar performance and extended oil change intervals.
Be careful before choosing an oil purely for its extended oil change interval capability. There’s more to it than just the oil (eg: more frequent oil filter changes, additional by-pass filters and/or regular oil analysis tests). If not done properly, you could damage your engine. More importantly, these oils are generally designed for heavy machinery operating under severe duty service conditions and have additive packages to meet CH-4, CG-4 or CI-4 API standards. As such, they’re not recommended for the 2LTE engine if it does not see severe duty service conditions. They also generally come with a hefty price tag which implies that it’s big business operating big machinery who can afford it.

Important Notes:
(1) Exception (3) above is not because of engine wear due to metal on metal contact, but because the 2LTE indirect injected diesel engine is a particularly sooty engine. Under severe duty service conditions, more soot is produced as a by-product of combustion. This soot is dispersed into the engine oil and held in suspension until you change the oil. Soot is acidic, and the longer it's in the engine, the more opportunity it has to increase the acid level in the oil by overpowering the pH balancers in the oil additive package. The result is it begins to eat away at the internal metal components of your engine which will increase wear and reduce engine life.

(2) The same rule should apply for all diesel engines, but to a lesser degree, for engines that are known to be less sooty (including 1KZTE of similar manufacture age; 1990 - 1994).