I have a 2007 Monte Carlo LT and it's been leaking oil for about 2 years. The oil leak started off small with a little bit of drops when the car is parked. I change the oil my self because I used royal purple for the first 30,000 miles and now I use Mobil 1. I think it might be my falt in over tighting the oil filter and bolt. The car is low to the ground and I've bottom out a couple time in the rain because the water fills up the pit holes. When the car is at 2000 miles 1000 away from a oil change it always needs a quart. The last 6 month the car has ben leaking a lot of oil and when I check the oil dip stick oil level is ok normal. 2 month ago the car needed 2.5 quarts of trans oil. When I look under the car it's clear to me it's motor oil being leaked because the color is brown. I hope some one out there can point me in the right direction before I take it to the dealer. I pay $26.99 for Mobil 1 at Walmart + 5 or 6 for the filter, that's why I change the oil my self. I took the car to the dealer the other day and they wanted $120.00 for a Mobil 1 oil change. The dealer to me charges way to much. I scared to take the car to the dealer :-(

 

Hello, welcome to the forum. Nice to have another 7th gen. Monte owner here. When your able put up a few pictures of her. Why is your Monte low to the ground, have you had it lowered? I'm always careful as can be on bumps and such because mine is lowered.

So you say it's motor oil because it's brown. Have you felt it and smelt it? tranny fluid thats due to be changed tends to be more brown than red, and will have it's own unique smell, different than motor oil. What does the tranny fluid on the dip stick look like, brown or red? Could have a tranny cooler line with a loose fitting. Is the fluid at the front of the car or directly under the engine / tranny area?

 

The Monte Carlo is stock and iam always careful going over bumps. The color of the tranny oil in the dip stick is dark brown. The color of the motor oil and tranny are almost the same 😬. The car just hit 80,000 miles and I want to change the tranny oil and radiator coolant. Thank you for the tip about smelling the oil I'll try it when I get home. The dealer is expensive so I stay away from the dealer. Reading other peoples treds I think I better take the car in before the problem gets worse. The car has 80,000 should I change the tranny oil, spark plugs, break fluid, muffler?

 

It never hurts to stay on top of the maintenance. Ask around at Auotzone, O'Reillys and other car parts places for a honest respectable shop to take your car to for work to be done. Most people at the counters tend to know a decent shop for you to go to. The dealerships make their money on repairs, and while they use brand name parts you will pay top dollar for their repairs.

If I had to pick a priority, I would have the leak located and repaired. Do the tranny fluid / filter change but not the whole system flush, brown is not a good color as it should be red, so it is worn out and will cause excessive heat build up due to it's viscosity being broken down. And heat is the enemy of our transmissions. Have them use a DEXRON VI transmission fluid for your new fluid. It takes a lot of abuse and is all GM recommends now.

The spark plugs are usually good for 100,000 miles. Make sure you only use AC Delco, NGK or Autolite's. Don't let them put in the Bosch brand as they tend to have performance related issues on our cars.

Brake fluid is something you should do every about every 50,000 miles or 3 years, so it sounds like you should have this done. What would be adequate is for you yourself to remove all the fluid from the resevior where you add the fluid, usually with a suction type of thing like a big syringe or such and save your self a few dollars. Remember or mark on the resevoir tank the old brake fluid level in the tank before you remove it, so you don't put to much in when you refill it. You don't want to make it to the full mark, or when new brake pads are added later it will force the excess fluid out and on to the ground, making an unnecessary mess. Already have your new bottle $7.00 bottle of brake fluid with you, add the new fluid bringing it back to the the same level as the old fluid was before you removed it. That generally blends in well enough to render the fluid in the lines good again. Thats the quick way if your not handy at bleeding brakes or not wanting to pay someone $75 to change your brake fluid.

Why a muffler, has your worn out already or are you going for a performance sound?

 

My Monte Carlo transmission oil leak was finally fixed. I did a transmission oil flush, new gasket and filter. My MC had two oil leaks one was fixed with a new gasket on the transmission oil pan. The second oil leak was fixed with a new transmission line connector that connects the tranny to a line that runs to the radiator.
*Transmission oil flush, new gasket and filter $160
*Radiator coolant flush $80.00
*2 New (Front) rotors, break pads on all 4 wheels and a new transmission line connector $360.00

 

Would that cause an oil leak that would take 3 months before the low oil pressure light comes on?

 

My oil pressure sensor/switch failed and started leaking right through the back of the sensor through the electrical connector. Access is made by removing the passenger right front wheel and the plastic cover.

 

Update on my oil leak. It turned out that the source of my leak was a loose oil filter. The last place that did the oil change never tightened it. So the car will never go back to that place again.

 

I'd be beyond furious. I get theres probably nothing you can do to get money out of them, but that could've damaged your engine since it ran out of oil (that low oil pressure switch trips extremely low so the engine essentially had near zero pressure while it was on).