Hello everyone. My name is David and I'm from Spain. I've been looking for a forum with knowledge people on oil and I just found it!. This looks like a great source of information. I tell you my doubt. I have 1991 Toyota Land Cruiser 4x4 truck. It has a 4.2 Turbo diesel engine that has run superb so far. Last owner had used 15-40 mineral oil and had changed it every 5000km. Two years ago, my mechanic told me to switch to 5-40W fully syntetic oil and change it every 10000km. Then a friend told me it was a mistake in such an old engine and I moved to 10-40 semi syntetic oil in the last change. The thing is that it has started using some oil (0.21l/1000km) since I switched to 10-40 semi syntetic, what I can understand as it's thicker than the 5-40. It didn't use a drop of 5-40 in 10000 km. So I've been researching these last days about the best oil to use in my truck. I've been told to look for a J-spec oil with JASO/DH-1 spec as it is an old japanese engine. The only one I could find in the spanish and english markets is the Texaco ursa TD 15-40W, with has some great features appart from having the JASO/DH-1 spec, but Texaco recommends it for use in heavy duty truck and bus operations. It allows from drain intervals up to 45000 km!. And the best of all is the price: 20 liters for 32 pounds (about 50 US dollars). Here is the data sheet (in spanish, I couldn't find it in english): http://www.texaco.es/es/docs/fichas_tecnicas/automocion/URSA%20TD15W-40.pdf And the UK distributor site: http://www.texaco-online.co.uk/index.html?lub2b.html There is a post in whatdieselcar.com forum from a guy that looks very knowledgeable in engines oils, called "Jon the combustion engineer" recommending this oil to use in a Citroën Xsara, so it seems it's not a problem to use it in small cars. He also explains the API rating, what is really usefull. According to that, this oil has a better quality (API CI-4), than a Castrol Magnatec that costs 4 times more (API CF). I don't understand it! This is the post: What Diesel Car | The Forum Till here, everything looks great, but in the next post, he states: "Once the lubricant has gone past CH it is classed as a SHPD - Super High Performance Diesel Engine Oil. I would warn however that extra duty oils can cause more harm than good if the vehicle is driven gently all the time and the brakes used little and the gears used to brake alot. This is because excessively gentle driving or long periods of idling lead to bore glazing and polish. Just shows that diesels are designed to work - and work hard!" This last thing is what worries me, as this oil is a CI-4, it's sure SHPD. I wonder what does he mean with "driven gently all the time". I also wonder if shortening oil changes would help with the bore glazing thing. What do you think?. I believe it looks like a great oil at a great price, and has the J-specs, that's what I was looking for, but the fact that Texaco recommends it for big trucks and buses and this bore glazing thing makes me hesitate. To make thinks unclearer, here is some literature: Here, it's stated that the SHPD oils causes bore glazing: Bore glazing In this article they say the SHPD oils create bore glazing but just on the running in period of a new or reconditioned engine, but then they recommend SHPD oils as they prevent cylinder bore polishing. http://www.ferobrake.co.za/ktml2/files/u...Consumption.pdf Here, there is a brochure of Gulf Western oil when they advertise their J-Power oil (with the same specifications as Texaco Super TD) that it "protects against bore glazing in stationary engines" http://www.gulfwestern.com.au/Web%20Images/GW%20Bochure_09_lr.pdf Here in Total Uk, it's said that bore glazing occurrs in early engine life. Glossary What do you think?, should I worry about the bore glazing thing in such an old engine or should I go ahead with this oil?. Any oil recommendation? Thanks a lot in advance.