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If it ain't broke, don't fix it? Which preventative maintenance is worth it?

Thank you all for your time.

I am trying to follow my manuals’ recommendation schedules. 2005 Chevy Malibu Classic (4cyl) and 2005 Chevy Equinox (6cyl, AWD). Both with 140,000 miles. Wondered your opinions on the cost/benefit of the following preventative actions vs. just leave a running car alone. I will state that I love having paid off cars that work, so I’m willing to invest in prevention.

  1. Should I start partial replacements of transmission fluid if I have never had this service done? Per the manual, transmission fluid service is only recommended under extreme driving conditions, none of which apply to me. I agree with the consensus here on the forum that trans-flushes are not necessary and possibly detrimental. However, many have mentioned a simple (partial) fluid replacement as a good idea. Drop the pan, change the filter, and replace any fluid that drained (~1/3-1/2 of fluid). Do I start doing that at 140,000?

  2. Replace spark plugs? Recommended changed at 100,000 miles. I have noticed some hesitations, temp. drops in RPMs, etc that may or may not be remotely related. Wondered if a simple change could (possibly, just maybe, might as well try and see if they) fix the issues.

  3. Had coolant system flushed in one, planning on doing the other. Both recommended at 150,000 miles.

Other than the above, have pretty much only changed motor oil, replaced engine air filters when dirty, and dealt with repair bills and brake/tire bills as they presented themselves. Haven’t touched steering fluid, brake fluid, etc.

Thanks all!

i would get new spark plugs.

i ll leave the tranny issues and other fluids to the experts here.

You’ve gone past the normal service intervals for the systems you describe.

Just drive the vehicles and when a major component fails replace the vehicle.


Preventative maintenance is not “fixing it”. PM is how you keep from having to “Fix it”. Yes, do the partial ATF change. If you have never changed the plugs, do them. If they were changed at 100k, they should be good now unless you used regular plugs, then you need to change them.

Do not flush the cooling system either. However both vehicles are way overdue for a coolant system change. Its 5 years or 150k miles, which ever comes first, and you are way over the 5 years. Get the specified coolant (Dexcol) or one of the universal long-life coolants and drain the block and radiator, then refill with the correct mix. Be thankful you haven’t overheated either vehicle yet, but as long as the system is working, don’t flush. But you will have to do the next coolant change a little earlier unless you mix the antifreeze with distilled water at 2:1 (67% antifreeze) instead of 50/50 (50%).

If you buy premix, do not dilute.

athada wrote:
I will state that I love having paid off cars that work, so I’m willing to invest in prevention.

This statement baffles me. Using the Equinox as an example, you were supposed to replace the coolant five years ago. You were supposed to replace the transmission fluid and the spark plugs 40,000 miles ago. You were supposed to replace the cabin air filter multiple times by now. If you want cars that work, this is not how to do it.

To answer your question, you can save a small amount of money by skipping scheduled maintenance. You then run the risk of paying a large amount of money (often more than you saved) to repair something that shouldn’t have needed to be repaired, although of course you could get lucky and get away with the neglect. In your case, I wouldn’t be surprised at all if you end up needing a new radiator at some point because this one corrodes. I also wouldn’t be surprised if you’ve been paying for more gas lately due to the spark plugs being overdue.

It’s your car and your decision, but on my cars the scheduled maintenance gets done on time.

There is an old saying that goes something like…You can pay me now, or you can pay me later.

When it comes to cars and their maintenance, this actually means…You can pay a lower cost now for preventive maintenance, or you can pay a substantially higher price–later–for the repairs that resulted from ignoring the maintenance schedule.

By not following a good preventive maintenance schedule with these vehicles, the OP has set himself/herself up for the latter situation of high repair costs. Once the horse has escaped, closing the barn door isn’t very useful, but if I was in the OP’s situation I would have ALL of the long-deferred maintenance done now, in the hope of delaying the inevitable repairs a bit longer. That may or may not work, but it is worth a try.

And, with the next vehicles, I would suggest adhering to the mfr’s maintenance schedule from the beginning, as it is invariably cheaper and this helps to reduce the chance of catastrophic mechanical failures.

I personally think that it’s never too late to start with maintaining your car properly.

Why just ignore it. Get your owners manual out and start now. It might save you a huge bill in the future.

Start with new Trans filter and fluid in both and because you will only get a partial fluid change, I’d do another filter and fluid change in 20K.

New plugs in both and PCV valves along with a good cleaning of the throttle body on both cars. This might clear up the hesitation that you feel.
And I’d try to catch up on the suggested maintainence items one by one.

Next time each gets brakes get the fluid changed out.


Even though you are behind on a lot of maintenance, it’s never to late to start…Change ALL the fluids, including the tranny, the spark plugs, all of it…Or, as Tester recommended, just drive your cars into the ground and buy new ones…

When you have all this work done, do NOT use a “Qwicky Lube” kind of shop. Instead, find a good independent shop, through recommendation by a knowledgable friend or from the “Mechanics Files” link above.

Preventive maintenance is really “failure prevention”. Other than those things that wear out such as brakes and tires, the maintenance prescribed is designed to keep the car running reliably.

Indeed, may posters here do more than prescribed, and change transmission fluid and filter very 30,000 miles, and coolant every 50,000 miles or 5 years.

I consult on industrial maintenance and with expensive monitoring equipement we can do “condition-based maintenance” which means that be ongong oil monitoring, we know when to replace it. This may not be practcal for the average motorist, although an oil analysis every now and then will tell you how far the oil has deteriorated. Compressors are analyzed to see how their effectiveness had deteriorated. If it has goen to 85% of new, the unit is definitely overhauled or replaced. On an old car, a compression check will show you the same thing.

I have had best results with 5000 mile oil & filter changes, engine coolant every 50,000 miles or 5 years, transmission fluid every 30,000 miles and spark plugs as per the owner’s manual.

Worn out spark plugs will cause misfiring, which affects fuel economy as well as foul the catalytic converter.

I’m firmly in the Do It Now camp. It is always best to assume you are “severe” duty. It is the conservative position to hold. “Over” maintenance never really hurts anything. You missed a few, like a tranny fluid change but now, change EVERY fluid, brake, power steering, transmission (as @Yosemite recommends) and get on with it. Internally clean the throttle body, maybe run a little Sea Foam though the engines.

At the same time, use the lack or car payments to save up for either 1) the large repair bill you might get on a 140K+ car OR 2) the new car (or 2-3 y/o used) you will need about 60K miles from now.

The important items are transmission fluid , changing/checking motor oil and not overheating for longevity in vehicle. Spark plug replacement will prevent a future breakdown and potentially correct your running issue.

Better late than never. Replace the transmission fluid first and then the spark plugs if you can’t do both at the same time. If you have no problems with the transmission, replacing the fluid may help extend the transmission’a life. If your fueleconomy hasn’t taken a dive and the engine is not missing, wait on the plugs. But both should be done.

yeah i will second almost all the experts.

better late than never. if you are lucky you will have these cars for a good long time if you start reg. maintenance now.

Thanks all for the helpful advice, and for the kick in the pants to get started. Didn’t mean to stir up the scoldy-pants… I just bought one of these cars and I wasn’t in charge of maintenance the first 140K. I am on the road, so the speak, to a le molittre maintenance education and awareness.

Any more input is likely appreciated. Awesome!

Just remember, Maintenance is not repair!

I’m in the camp that in your case, you have proved that many things can be delayed and you continue to roll down the road.
You have received good advice here but keep in mind that you still have to do a cost/benefit analysis.

If you bought the car for $2500 and want 3 years life out of it, you can still get by and take a slight risk of dealing with a couple of the top priorities and let the others surface before repairing/maintaining(cuz the problems may never appear)

Many people neglect their cars and do come out ahead $$ wise. Now if you want 6-10 years out of this same car, absolutely follow the advice as prescribed.

An update:

Malibu - a friend is helping me change the 4 plugs (no wires on this one). I received a great recommendation for a reputable, independent shop where I just moved. They recommended that if I have not serviced transmission fluid/filter up to this point (140K miles), then leave it alone. I don’t understand all the details, but having switching over to new fluid after the parts are “used” to the old could cause tranny problems. I took them turning down work ($) as the sign of a well-run shop. I understand that others might have a different point of view.

Equinox - ditto on tranny. Might pay to have the plugs done. Coolant will be flushed. Cabin air filter replaced.

Thanks again!

that is bull about the the tranny. now is exactlu when it would help the most. IMO


"They recommended that if I have not serviced transmission fluid/filter up to this point (140K miles), then leave it "

That is extremely bad advice

Since you have 140k, and haven’t serviced the tranny yet, and it’s still alive, count yourself lucky

But don’t keep pushing your luck

Here’s what to do

Drain the fluid
Drop the transmission pan
Clean the pan
Replace the filter
Reinstall the pan, using a new gasket
Fill the transmission using the correct fluid . . . Dexron 6, probably

Do NOT let anybody talk you into a transmission flush

And do NOT let anybody talk you into using generic/multipurpose fluid

Good luck!