What fluids to check at 100k miles?

Messages
3,742
Location
Northern California, USA
My truck (2001 GMC Sierra Z-71 4x4) will be hitting 100,000 miles next year (summer). I just think it is a good idea to know what is going on in my truck so I was thinking about getting some of the fluids analyzed. What fluids should I get analyzed? I do NOT plan on getting an analyses on the brake fluid or the power steering fluid. I flush the brake system every year, and I change power steering fluid when I do an oil change. I was think about getting the transfer case oil (autotrack) checked and the engine oil. There is also the front and rear differential fluid and the engine coolant (LowTox). I am figuring to spend up to $100 for all the tests.
 
Last edited:
Messages
252
Location
Austin, TX
Originally Posted By: HTSS_TR
I wouldn't spend $100 to analyze those fluids, I rather spend that money to buy better quality fluids.
+1 Just buy good stuff or go with fluids from the dealer
 
Messages
9,103
Location
Houston, TX
Originally Posted By: HTSS_TR
I wouldn't spend $100 to analyze those fluids, I rather spend that money to buy better quality fluids.
+1 ^^^^ this. If those fluids have never been changed, I would change transmission, front and rear differential, and transfer case fluids. You can always take samples of the fluids and have them analyzed at a later date if desired.
 
Messages
5,529
Location
Florida
What is the reason to get those juices analyzed anyway? Are you planning to take the truck to 1 million miles? If so, then it makes sense to see how those parts are working / holding up. Otherwise, spend the money on higher quality lube and spend the rest on a case of Cheers2
 
Messages
1,107
Location
CA
While the analysis would be interesting to determine frequency, my guess is that the manufacturer recommended intervals have been arrived at after better analysis with a conservative margin of error for non normal service. As has often been said, you change oil before it loses the properties that are the reason for adding it in the first place. The same goes for the other fluids. It seems you may be changing your brake fluid a little too early. The most recent formulations are well above minimum federal requirements and manufacturers who specify a change interval do so at the 2 to 3 year mark. I would say the same for power steering fluid. My car's maintenance schedule does not call for this to be changed and I haven't done so (car is 7.5 years old). I looked at the color on a piece of kitchen towel and it isn't bad. I will be changing it soon, because it's better to be safe than sorry, but every year is overkill. I would agree with those who recommended having the transmission fluid changed, but again, do it at a sensible interval. We use a lot of chemicals and resources in this world and I think we can all make a difference by not over maintaining our cars. We're already making some kind of difference by making sure we make them last as long as possible. (Case in point, I spent $65 extra to have my rotors resurfaced because on balance they had enough life left and I don't want to be responsible for the production of an extra set of rotors in China. I hear too many people say that when I change my brake pads I change my rotors because they are so cheap anyway. Resurfacing your rotors is good for American jobs and good for the environment!)
 

Loobed

Thread starter
Messages
3,742
Location
Northern California, USA
I think I use good fluids. I have Amsoil Severe Gear 75w-90 oil in the front and rear diffs. I use GM Autotrack fluid in the transfer case. Castrol DOT 4 brake fluid. Castrol Dex 6 tranny fluid (which gets drained and refilled once a year - 4qts from a 12qt system). Prestone LowTox coolant. Name brand synthetic engine oil (Pennzoil, Quaker State, Valvoline, Mobil-1, Castrol Syntec, G-oil, etc). I guess I'll save my money
 
Messages
609
Location
New Jersey
I don't think that "save your money for higher-quality fluids" is a logical tradeoff. It just is not one or the other. I encourage you to change all fluids with high quality fluids. Some fluids are not worth analyzing as they really don't tell you much about the system's health,(brake fluid, Power steering fluid, transfer case fluida) and even if they did, they would not forestall or eliminate the possibility of mechanical failure in the subystem. But engine oil analysis really gives you a clear picture on whether your engine is going the long haul- definitely do that. Good Luck.
 
Messages
1,107
Location
CA
Originally Posted By: Loobed
I think I use good fluids. I have Amsoil Severe Gear 75w-90 oil in the front and rear diffs. I use GM Autotrack fluid in the transfer case. Castrol DOT 4 brake fluid. Castrol Dex 6 tranny fluid (which gets drained and refilled once a year - 4qts from a 12qt system). Prestone LowTox coolant. Name brand synthetic engine oil (Pennzoil, Quaker State, Valvoline, Mobil-1, Castrol Syntec, G-oil, etc). I guess I'll save my money
If you're doing 10,000 miles a year (100k 2001 MY), then I'd say you could go 2 years on the brake fluid. On the ATF, I would suggest verifying the manufacturer procedure and interval since you are only changing out a 1/3rd of it every year. This means you will always have old transmission fluid. It would be better to do the full 12qts every 3 years instead of 4qts every year. This would cost the same in fluid, less in time / labor and you'd have newer fluid all of the time. Do it every 2 years if you are worried.
 
Messages
1,107
Location
CA
Originally Posted By: dparm
*Maybe* the ATF. Other than that I wouldn't bother, just replace the fluids with quality stuff and live your life. :-)
Lol! Said by someone with 4 completely different brands of oil in 4 cars (leading me to believe they've done careful research on the topic) Come on, the reason we are all here is that we don't have a life! Life itself is a fluid experience after all.
 
Last edited:
Top