No leaks that i can find but it's cold and snow on the ground so not so easy to check everything. Isuzu customer relations in the U.S has verified that they are now recommending the switch for vehicles with higher mileage. The things one learns these days.
Thanks to everyone for the input. Have a safe and happy holiday.

One other thing that i have noticed: the short time I have owned a 98 trooper I started to use 10% ethanol blend. This seemed to have a noticable reduction in oil burning.

Considering there is no good synthetic 5w30 oil in USA (exept for Amsoil) 15w40 (which is a diesel oil) actualy does help with oil consumption.

I'm using 1qt every 300-400 miles when using 5w30 Castrol Syntec or Mobil1.
After switching to Shell Rotella 15w40 i'm up to 1qt every 1,000.

Real synthetic oils available in USA include (but not limited to) Castrol Syntec 5w40 (formulated for Volkswagen turbo engines), Mobile1 0w40 (European formula), Amsoil (all of the grades), Dello400 synthetic 5w40 (Diesel) and Shell Rotella Synthetic 5w40 (again Diesel).

Every other "synthetic" oil on the market IS NOT a true synthetic (Mobil1 being Class4, comming realy close to a true synthetic, but still not as good as Class5 oils listed above).

Just my $.02

Glad I dont have an oil burner. I've been using Mobil 1 5w30 since I bought it last year and mine only uses about 1qt or less per 3k miles. I would like to use Amsoil if it wasnt such a pain to get. Since I dont do my own oil changes any more its just easier to go with Mobile. I have Amsoil in the tranny and xfer case though.

Rubo, you did not provide a definition of a "real" synthetic oil. Usually, it means that the oil base is pure syntehtic, plus some additives. It's a myth that all good Europian oils are "pure synthetic". They just have more additives than an average USA oil. I had a book by a Russian oil specialist with detailed study of the modern oil technologies. You will be surprised but an average good Europian oil has a rather mediocre oil base. They just add good extensive additive packages.

More narrow definition of a "good synthetic oil" is "oil mostly of 'ester' base". I am almost 100% sure that no oil listed by you has mostly ester base. There some Europian brands with ester bases but they are really expesive.

And you know, there is an ester-based oil in the USA. I mean the "Red Line". I used it, it was a great oil, but I just did not feel the difference. Our motors are too simple for those sofisticated oils.

As for the 15W-40, take into account, that if you have more additives, then you have less base (which is the "lubricating" part of oil). So, this is a double-ended thing.

My engine works fine with "simple" Mobil1 5W-30.

I have some updates.

First, the "real" Europian synthetic oil brand name is Motul, with excellent base compound. But this oil is virtually unavailable in USA, and also it's usage in the stock cars&trucks is questionable.

Second, I decided to sacrifice my vallet for the common good, and yesterday, when performing my Axiom service, I used the "europian" oil mentioned by Rubo - 0W-40 Mobil1, with BMW and VW certificates. I'll report if I see any changes to the oil consumption. Currently, the engine uses about 1qt of 5W-30 Mobil1 oil per 3000 miles. Let's see if "advanced" oil has anything to do with the consumption in our case.

My small Mazda uses no oil at all between 7500 intervals, even when I use a cheapest oil.

A few years ago I was also researching "Pure" synthetic oils for auto use. I cant remember the site but it had tons of info, I will try and find it again. But I do remember that it stated that you cannot mix a "Pure" synthetic oil with any of the so called "fully" synthetic oils we can find here in the US such as Castrol and Mobil as they are not really "fully" synthetic. To actually use a "Pure" synthetic you would need to completely flush the whole system of the old stuff to get any of the benefits of the "pure" stuff and the stuff ain't cheap. So where are the chemists on the 'Wire' when you need them ?

As far as testing the present synthetics in the US I have also tried most of them and found that my Rodeo burns any of the Mobil stuff faster than any of the Castrol stuff, Castrol 5w-50 seems to do the best for me, even over the Dinos.

Once in a while I top off my 3.2 with oil that is so generic, it just says "oil" on it.