Ive seen it posted that some TX guys on these forums are die hard Castrol fans: i was too please read.
Hey guys, all ive ran i Castrol GTX in my cars for the last 8 years, i have it in my GSXR which i used to race up till last year because of work, anyways i was the biggest Castrol fan out their. And it has always worked great for me so i cant say anything against it, and my GSXR raps 13,800 rpm for 1.75 miles down the superstretch on the Daytona Int. Speedway, so its damn good oil, however when i got my DS and started taking it to the dunes in 100 plus temperature of TX i need good oil, i did run castrol for the first three oil changes than i started doing alot of reaserch and if you go to the specs, graphs on the more detailed websites the truth is in black and white. Castrol is always up there with the top dogs , but Quaker State beats it in every category every time, that blew me away, and some of the Valvoline specialty oils were off the chart with amazing numbers. So anyway after about 10 hours of hard reasearch, and 9 years of using Castrol, i did switch to Quaker State for my Jeep, and im going to run Valvoline Race line oils in my GSXR and My DS, these are not my opinions, these are the facts, hope you can all benifit from my research.
However i think the Castrol, if you chose to keep using it will do you just fine, i know from experiance.
One last note for the guys in TX with the DS, you need to be running 20W-50 not 10W-40, because of the temp ranges we have down here, running the wrong weight(too thin) of oil in this TX heat is doing way more damage than any differece in brands would make.

Rob.

ps. this doesnt even start the topic of synthetics, which i dont recomend after doing the reaserch on them, not in your DS at least

 

I have used nothing but Valvoline forever. I do not believe in addatives for oil or gasoline. I use only Chevron gasoline.

I use Valvoline Durablend in my 5.0L Mustang and PU, and Bronco because synthetics do cut down on engine wear when the engine is first started and that is when the majority of engine wear is done. After talking in length with Valvoline factory representatives, I started using Vavoline Max-Life in my daughters 88 Bronco II with 155,000 miles on it. It decreased the oil consumption, I am impressed.

Not to be a comercial, but, Valvoline is the number one choice of top mechanics.

 

On these tests were they tested using 20w-50? Where in Tx are you?

 

I use Valvoline Durablend in everything I own, even the lawnmowers, except the DS. I use Durablend in my Arctic Cat, Chevy, the Kohler v-twin in my tractor, etc., but I do use Honda HP4 in my DS. I do believe that in this day and age, it is actually possible to engineer products for specific purposes, and I'm not going to worry myself with a few saved dollars when changing the oil in a quad that I have over $9,000 invested in.

I like the fact that the Honda HP4 was made for high-revving wet clutch applications, unlike any of the other motors I mentioned above. If we can put a man on the moon, we can make an oil for a specific purpose. If we can make a motor like the 653cc Rotax with an aluminum cylinder and coat it with special alloys for wear resistance, all in the name of better cooling at high revs, we can make a purpose built oil too. I've not seen lab testing results on this oil compared to others, I'm just going on faith here. If I ever do see results that show no advantages, then I'll just start running Durablend in the DS too.

 

Just doing a search on "oil facts" or "oil comparison" etc on Yahoo would be a great start on the never ending search on which oil is best. some sites to read:
http://www.vtr.org/maintain/oil-overview.html

http://subtopics.freeyellow.com/Oil.htm

that will get anyone started in become well versed on oil.
good luck
Rob.