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MB GPW G503 WWII Military Jeep changing of the oil and oil filter WW2 Restoration

It is not difficult to change the oil and oil filter for your G503 WWII jeep. It can be a little messy, but if your prepared, you can do this yourself and save a little money.


This article applies to both Willys MB and Ford GPW WWII Military Jeeps 


Before changing your oil, you want to make sure your oil is warm so that it will drain better. Here in Southern California I will warm engine temp to about 140 degrees or about 10 minutes of idling.

1. Before changing your oil, you want to make sure your oil is warm so that it will drain better. Here in Southern California I will warm engine temp to about 140 degrees or about 10 minutes of idling.

You will need to a have a catch pan of some sort. Here I have an oil catch pan which will hold about a gallon and half of fluid

2. You will need to a have a catch pan of some sort. Here I have an oil catch pan which will hold about a gallon and half of fluid

Place the oil catch pan under the oil plug. It gets kind of windy here so I adjust the pan based on the wind and how I estimate it blowing the oil around.

3. Place the oil catch pan under the oil plug. It gets kind of windy here so I adjust the pan based on the wind and how I estimate it blowing the oil around.

Remove the oil pan plug by turning the plug counter clock-wise.

4. Remove the oil pan plug by turning the plug counter clock-wise.

Twist the pan plug with your hand. Try not to drop the plug in the pan, and twist fairly quickly as the oil will start coming out, and depending on how warm your oil is, it can burn you.

5. Twist the pan plug with your hand. Try not to drop the plug in the pan, and twist fairly quickly as the oil will start coming out, and depending on how warm your oil is, it can burn you.

Let the oil drain into the pan. While this is draining, I will head over to the oil fitter and prepare to remove it.

6. Let the oil drain into the pan. While this is draining, I will head over to the oil fitter and prepare to remove it.

Remove the oil filter housing lid. Unscrew counter clockwise.

7. Remove the oil filter housing lid. Unscrew counter clockwise.

The oil filter lid will most likely have some oil on it. I will let it drip for a bit before moving it over to a towel for cleaning.

8. The oil filter lid will most likely have some oil on it. I will let it drip for a bit before moving it over to a towel for cleaning.

Here I will put a couple baggies from the grocery store to immediately transfer the old oil filter into it. Trying to avoid spilling oil all over the engine and ground.

9. Here I will put a couple baggies from the grocery store to immediately transfer the old oil filter into it. Trying to avoid spilling oil all over the engine and ground.

I quickly put the old filter into the baggies, and tie it up for disposal at our approved Oil disposal location here in town.

10. I quickly put the old filter into the baggies, and tie it up for disposal at our approved Oil disposal location here in town.

You see after taking out the filter you still have about a quart left of oil in the filter housing. You will want to remove this.

11. You see after taking out the filter you still have about a quart left of oil in the filter housing. You will want to remove this.

12. There is an oil plug on some filter housings down at the bottom. If I drain from this drain plug I will get oil all over the engine and ground. So I remove it by dipping a small cup into the housing and set my drain container right next to it. and start scooping out the oil. I will do this all the way down to the bottom and then wipe out the filter housing and check for debris.

Here you see the filter housing is empty and there is no particles in the housing.

13. Here you see the filter housing is empty and there is no particles in the housing.

Install the new filter into the filter housing. You can use the following Oil Filter elements. NAPA 1100, Purolator PD51R, WIX 51100, AC P115 You can find it here at Napa Auto

14. Install the new filter into the filter housing. You can use the following Oil Filter elements. NAPA 1100, Purolator PD51R, WIX 51100, AC P115 You can find it here at Napa Auto

Oil filter sits down snug in the housing.

15. Oil filter sits down snug in the housing.

Remove the old oil filter seal from the lid, and prepare the new seal. I will coat the new seal with a little oil before placing on the lid.

16. Remove the old oil filter seal from the lid, and prepare the new seal. I will coat the new seal with a little oil before placing on the lid.

Clean the lid around the edges thorougly before placing the new seal on. Crud builds up on the edges of the lid, so be sure to wipe it down clean before installing the new seal.

17. Clean the lid around the edges thorougly before placing the new seal on. Crud builds up on the edges of the lid, so be sure to wipe it down clean before installing the new seal.

New seal installed, now place the lid on the filter housing and tighten up.

18. New seal installed, now place the lid on the filter housing and tighten up.

Prior to installing the lid you should inspect the copper washer and replace if needed. These are pretty weak so replacing them is common

19. Prior to installing the lid you should inspect the copper washer and replace if needed. These are pretty weak so replacing them is common

I place pipe tape around the plug thread to help stop leaking. I have drips that come from this plug, so I add thread tape to help stop that from that area.

20. I place pipe tape around the plug thread to help stop leaking. I have drips that come from this plug, so I add thread tape to help stop that from that area.

Install the bottom plug back into the pan. Tighen clockwise

21. Install the bottom plug back into the pan. Tighen clockwise

The TM's call for 30 weight oil. I use 10w30. Stay away from the higher viscosity oils like 20w50. Add Oil checking the amount on the dipstick. Its a little over 4 quarts.

22. The TM's call for 30 weight oil. Stay away from the higher viscosity oils like 20w50. Add Oil checking the amount on the dipstick. Its a little over 4 quarts.

23. After I put in 4 quarts I will check the level. If it shows near "full" I will go and start the engine. Remember your filter housing is empty, so it will suck an additional quart. So you will have to add some more oil after you let it idle for about 10min. While idling, you want to check for leaks around the oil filter lid. If the lid does not have a good seal, it will start leaking. Some owners will mark on the dip stick the level of the 5th qrt prior to idling so the know the level with a filter change.

24. Ok, jeep is done, now I need to be responsible for the environment. I pour the oil into a container I will take to a local Auto store that accepts used oil and oil filters. Here Kragen Auto accepts used oil.

At the Kragen Auto store they will have a large container in the store for you to dump your oil and dispose of your oil filter. I also give them any rags that become saturated with oil. Job completed!

25. At the Kragen Auto store they will have a large container in the store for you to dump your oil and dispose of your oil filter. I also give them any rags that become saturated with oil. Job completed!



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