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Oil for Jeep Grand Cherokee 2000

We have a Jeep Grand Cherokee 2000 in excellent condition. We have been using it to tow a 3000 pound travel trailer. According to the manufacture this is well below the limit that it is capable of. We have changed the oil to Pennzoil Synthetic Oil. But since then we have noticed that the engine is sluggish when we are towing. What is the best oil to use for this model of vehicle while towing?

If the weight of the previous oil and the new synthetic are the same - then there would be no noticeable difference in power. Claims made on TV ads aren’t backed by any science, oil is oil.

Your Jeep is getting old and your problem may not be the motor at all; it could be the transmission. Make sure the motor has recently changed spark plugs, a nice clean air filter and is running smoothly.

For the transmission; when was the last time it was serviced? Towing is deadly tough on transmissions; harder on the tranny than the motor. If your Jeep doesn’t have an auxillary transmission cooler you may want to consider having one installed. Did the Jeep come with the optional “towing package”?

Other possibles are winter gas which has more ethanol, or the motor could be getting old and losing some compression due to age and wear and tear.

Whatever it is, I don’t believe it is the oil.

No matter what oil you use, the engine will not become “more sluggish”.
There must be some other reason; a good mechanic will find the cause. When you switch to synthetic in an older vehcile, especially when towing, don’t use a very light grade; synthetic is very slippery and the engine will use oil.

Synthetic oil is great for heavy engine loads and high temperatures. For typical towing I would use a 10W30 full synthetic, such as Mobil 1 in the summer months, and change it to a 5W30 in the winter.

If you have not been changing oil in accordance with the manual all these 10 years, you could have an engine coking up on you. Please tell us what past maintenance the vehickle has received.

If you live in the South and don’t go North, use a 10W30 synthetic all year round.

What engine? 4.0 6 or the V8? Both are capable of towing 3000lbs.

You didn’t state the mileage. Is there any consumption?

I too would not attribute the oil to this change in performance. I don’t necessarily agree that you cannot perceive differences in oil (try going from 5w-20 to 20w-50 and see if your engine feels the same until warm up) I would think that anything in terms of parasitic losses would be way over masked by the load you’re pulling.

The sluggish part can be lots of stuff. Your cat can be clogging up.

Thanks so much for your replies. They have given us a lot to think about. Maybe this clarification will help us narrow the field. We have owned the jeep ourselves for the entire time and it has been well maintained with all the oil changes and tune ups at the appropriate times. For a 10 year old car, it definitely is in great shape. The only time we feel a difference is during towing. Because it is our third car, it is garaged in the winter with battery removed. We only use it for the summer for towing and trips to the lake with the kayaks. It has a V6 engine and a towing package. It’s nearing 100,000 miles but hasn’t hit yet. Besides being sluggish during towing I forgot to mention that we have overheated in slow traffic twice. Does that change things? My husband really should be writing this but I type faster. I have been forwarding him at his work all your responses, though, and we do appreciate the help.

As an owner of a Jeep Grand Cherokee I can add a little insight here. The oil has no bearing on the sluggishness of your Jeep when towing or not. The Jeep weighs about 4K so your towing a 3K trailer is at the upper end of it’s towing range. I know the owners manual says 5K but that’s unrealistic. When towing anything you want the tow vehicle to weigh more than the towed vehicle. This is just a matter of safety. I worked in the RV world as a parts manager and RV mechanic and it was a well known fact that V6 engines and large trailers don’t mix. The Jeep can tow the weight but a 4-way sway setup is highly recommended. You must never tow with the transmission in “overdrive”. That would cause the transmission to “hunt” constantly for the right gear. That could account for the sluggish performance when towing. I hope this helps. Go Jeep!

Overheating in slow traffic can be a clue. Are there electric fans on this vehicle or a belt driven fan just behind the radiator, or both? Fans not kicking in with the AC on could cause overheating. At the worst end of things you could have a blown head gasket. If you are needing to top off the coolant there maybe coolant going out the tailpipe. Coolant in the oil, or oil in the coolant are other signs of head gasket problems.

You might just find a 10 year old SUV is just showing its age. You stated it was maintained, but does that include regular transmission services? Motors generate the power, but getting that power to the wheels is the job of the transmission. Lack of power problems means the power at the drive wheels isn’t up to par and that can be the transmission’s problem especially if the motor is running smoothly and seems “normal”.