Piston Slap: RTFM FTW

It actually comes with a little book too!

Patrick writes:

Hi Sajeev,

Avid daily reader of the site but infrequent commenter… Pony Cars and old Volvos sometimes drag me out of my shell but I have a couple questions about my wife’s car and I wanted to see what you and others might think.

We’ve got a 2007 3.5L Impala with 60,000 miles on it and it is due for an oil change and checkup:

1. Am I crazy for trusting the car’s computer to tell me when to change the oil? The car monitors oil life and reports a % of oil life remaining and nags me when it’s time for an oil change. The owners manual doesn’t specify a mileage interval instead advising to change it when the car’s info center says it’s time. It typically runs from 8K to 11K miles between changes so far.

The dealer would rather us get it changed at every 3K and are so desperate to get their fix of oil change traffic that they offer a “free tires for life” deal if you stay on the 3K schedule with them. Factoring in the cheap tires they get at cost that they’d slap on there, they’re most certainly coming out ahead (which is why they do it, of course); factoring in the extra services and the mounting and balancing fees for those free tires, it’s probably a wash for me so I’ve declined and followed the car’s schedule instead of there’s as

I’d rather save up for that next set of tires than have to go in to the dealer 3 or 4 times as often.

Now, I know I don’t have to take it to the dealer and while I do almost all of my own service, repairs and upgrades on my car, wrenching on our utilitarian transportation-mobile isn’t nearly as rewarding and I don’t mind throwing the Chevy place a bone every once-in-a-while, especially since their service isn’t much more than the quicky oil change places and, theoretically at least, they should be intimately familiar with this generation of Impalas – plus if and when it comes time to trade it in or sell it, I’ll have nice official looking dealer records to go with it.

I figure GM did their homework with the oil monitoring system and I’m comfortable with longer oil change intervals – I do 6K ~ 7.5K on my Mustang (’96 GT) which has 130K+ on it and oil still comes out clean and when I had the valve covers off last year, the top of the heads were clean as a whistle. With the Impala PCM monitoring temps and driving usage and whatever other variables it factors in, I’m willing to let it ride a little longer if GM says it’s OK. Have you heard anything that would give me reason to believe otherwise?

2. When I realized 60K was coming up, I rushed to the owners manual to see what expensive work the dealer was going to want to do – then I remembered this wasn’t a European car and there was nothing other than greasing door hinges and locks and inspecting a few wear items that needed to be done. I did notice that the book calls for a fluid replacement at 150K miles for the 4T65-E transmission (or at 75K for severe duty). After reading some of auto transmission horror stories here but not being aware of any endemic problems with GM’s transverse V6 transes is 150K too long to go, should I plan on doing that sooner? 100K, 125K, if we still have the car that long or is GM pretty close to the mark on that?

Sajeev answers:

I never thought that answering a GM W-body question would be a breath of fresh air in my Piston Slap queue, but well, here we are. Patrick has valid and relevant questions to anyone with a less than desirable ride that does the job and keeps you mobile. You know, cars for the vast majority of us!

So let’s do this thing:

Question 1: by all means, ignore the dealer when they pull the “free tires for life” and 3k oil changes. Like you said, I wouldn’t leave them entirely, as their pricing should be comparable to the quickie oil change places, but you need to get the playing field level: remind the service writer that you’re familiar with the phrase RTFM. And you expect them to treat you accordingly. The “do this to be more proactive” tactic you mentioned works on some people, and that’s fine. But that’s obviously not you or anyone else here. It’s all about treating the customer with respect.

I trust that oil life meter after years of questioning it via dipstick eyeballing. Now that I run synthetic oil (in cars that never officially required it), I change the oil after about 180% of its life: that is, resetting it once and then changing it when its 80% used. It seems like the smartest way to not waste good oil, and my driving conditions merit it: lotsa traffic, heavy engine loads (aftermarket stereo, A/C) and brutal Gulf Coast summers. The 180% mark turns into 6000-8000 miles of my commute. Which is fair for synthetic oil.

It works for me, maybe I should take my used oil examined to a lab to prove it to everyone…but I don’t really care since it’s been working for well over 175,000 miles on my very, very healthy Lincoln Mark VIII motor. Healthy enough to let me (cautiously at first) trust the life meter on other cars too. More to the point, your driving conditions can and will vary.

Question 2: there are no endemic problems with this GM transaxle that I know of, but I would still change the fluid before it hits 100k out of principle alone. Again, this depends on your driving/climate conditions, but my gut tells me you should change the fluid according to the severe duty schedule in your owner’s manual. Transaxles in general deserve the “severe” fluid service schedule, and this Impala sounds worth it. Be it a flushing machine or the conventional drain and filter replacement, just make sure all the fluid is changed…don’t let old fluid rest in the torque converter and mix in with the new stuff.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.