Is it better to use High Mileage oil or a thicker conventional oil such as 10w-40 or 5w-40 in a high milage car?

I just purchased 1996 Land Rover Discovery with 175k. Going to be doing my first oil change this week. Not sure what type of oil has been used in the car before. I have heard that thicker oil will help older vehicles not leak as much. I live in Michigan so the winters can get pretty cold. so should i use a high milage oil (5w-30 or 10w-40) or conventional thicker oil (5w-40). The owners Manuel suggest the following

14 To 95 F......10W-30

Above 14 F......10W-40, 10W-50

Above 32 F......15W-40, 15W-50, 20W-40, 20W-50

Below 14 F......5W-20

Below 95 F......5W-30, 5W-40

7 Answers

  • ?
    Lv 6
    4 years ago
    Favorite Answer

    It is better to use the oil indicated for the car even if it is high milage. a heavier or thicker oil will not lubricate the engine properly because its too substantial to travel through the oil line and oil pump since they are not designed for it. It will cause excessive wear in the engine. if the vehicle calls for light synthetic, 5w-30 will be compatible (even the dealership will use 5w-30 in a car that calls for 0/5w-20) but do not use anything heavier or thicker else you make the problem worse. Using heavier and thicker oils will also cause oil barriers to form inside the motor where it cannot flow into all the parts properly like the thinner oil does.

    do not use any of those 15, or 40 weights!!! the motor reaches the same operating temperature regardless of the oustside temperature. there is no need to change oil weight due to climate. All that you may have to be concerned about is a dry start during the winter or if the car sits for a long time. if you are concerned about a dry start, add a product such as lucas, which makes the oil sticker without making it thicker or heavier. If its synthetic oil, use the synthetic version. replace 1/2 to 1 qt of the oil with it.

    use 5w 30. that vehicle uses a roller cam, not a high friction flat tappet cam so it does not need any of those high mileage zddp oil additives, like STP. all it needs is "high mileage" oil because that type contains conditioners for the seals that help them not leak so much. If you do not want to buy high mileage oil, regular oil works just fine but you can also buy the seal conditioners separate in their own bottle and just add it to any oil of your choice. it can be hard to track down high mileage versions of some synthetics. And it doesn't really matter if you want to use conventional or synthetic. if the vehicle is leaking pretty badly, synthetic could be a waste of money since you'd be topping it off so often. Synthetics do lubricate better and last longer though.. and they don't sludge up. it does not mater if it has always used conventional or the other until now. you can go back and forth between using synthetic and conventional or even mixing them together, it doesn't harm anything.

    if the vehicle is also burning oil due to being high mileage, a thicker or heavier oil will make the oil burn off faster, not slower

    the only other thing you may want to tweak on for an oil change in a high mileage vehicle is using a solvent as motor flush during oil changes (or doing a piston soak but that's a whole 'nother thing). you can use a whole or half a can of sea foam in the crank case as a motor flush to help clear out carbon that contributes to oil burning or compression issues. Youd add it to the crank case with the old oil (make sure oil is at safe level, if not between the safe zone on the dipstick, top it off) and let the car idle for about 5 minutes but no more than10. do not drive it, just idle. then drain old oil and change oil filter and fill as usual.

    if the engine gets sludge in it, it can be flushed out without using an aggressive solvent treatment. a weekly oil change serves as a motor flush in regards to sludges or mud.

    Source(s): I have high mileage vehicle that used to burn oil. I have second 50 yr old vehicle with 30 yr old motor that's leaking so bad its paving the road, it uses 5w-30. oil is cheap, if it leaks just top it off... using wrong oil can harm the engine which is very expensive to fix. the leaking doesn't harm the engine. Seals are not that hard to replace, if you have the confidence to do your own oil changes maybe sometime down the line you would like to replace those leaking seals.
  • 4 years ago

    You should never use "thicker oil". The hydraulic lifters will get damaged and the connecting rod and crankshaft bearings will take longer to get oil pressure an cold start ups. Valvoline High Mileage oil is the way to go. Do your oil and filter changes every 3,000 miles. I've reached over 275,000 miles on my last two Pontiac's and the oil never got black!

    Source(s): Mitsubishi Master Tech
  • JetDoc
    Lv 7
    4 years ago

    Stick with the grade of oil that is recommended by the manufacturer. If the engine is NOT leaking or burning oil, then all those different oil weights will just give you a headache. With 175k miles on it, I would NOT recommend using a synthetic oil in this engine, as synthetics tend to break up sludge in the bottom of the engine and MAY open up some leaks or reveal other problems that have not been apparent.

  • 4 years ago

    Use the viscosity recommended by the manufacturer. So called high mileage oils have additives that claim to help older engines. I can't say if they help. but I KNOW using a heavier oil does more harm than good.

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  • John
    Lv 6
    4 years ago

    High millage cars it have lower compression in the piston and rings ,which mean it may oil leak in to the top of the pistons ,which will lower the performance of the engine .

    For such manner you need to use synthetic high performance oil and add 1 STP oil to increase the compression of the engine .

  • 4 years ago

    brave bid buying an old landie ..they are not the most reliable vehicle ...built just down the road from me ..hope yours has service history ..always buy the best oil you can afford ..especially on an older motor ...get synthetic for a diesel in uk we only change our oil every year ..not like the states should easily be able to go 10,000 miles between changes vans go 18,000 miles ...if it get really cold there and its not got a block heater ..we dont have those ..then 5-40 would be good ..but too thin for a summer ...if garaged then 10-40 is good all year round

  • alan
    Lv 7
    4 years ago

    continue to use the oil that is required,

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