Why is My Diesel Oil Light On?

Aug 22, 2020 | Diesel Maintenance

While you may not see it very often, the oil light for your diesel truck coming on could be a sign of a problem and could cause you to panic. It can be hard to tell right away whether the light coming on simply means you are out of oil, or whether there is a bigger problem, like an oil leak. The most common reason for the oil light alighting on your diesel truck is due to low oil pressure; there could be a few different problems behind this, such as low oil, dirty oil, or an oil leak. Let’s take a look at some of the reasons why your oil light may come on.

How Do I Know if my Oil is Low?

Unfortunately, as nice as it would be, the oil for your diesel truck is not going to last forever, and you will eventually need to replace it to ensure all of your engine’s parts are well lubricated to keep them running properly. The majority of diesel trucks do have monitoring systems for oil that will alert you when it is beginning to run low, but not all of them do; if your truck does not have an oil gauge, or if you just want to be on the safe side, you can check the oil directly at the source. If you notice that your oil light comes on when you are braking, that can be an indicator that your oil is low as it will be all running to one end of the tank, away from the oil sensor, as you brake. You may have enough to keep you going for a short while, but you should also action this quite quickly to avoid running too low.

Your owner’s guide should walk you through a step by step of how to do this. But, for most trucks, you need to pop the hood of your truck and find where the truck’s oil dipstick is – you will usually be able to locate this due to their yellow or red coloured handle. Always have a clean rag or cloth to hand so that you can wipe down the dipstick to avoid contaminating any oil that may be in the tank. Insert the cleaned dipstick into the tank and remove it to get a more accurate oil reading. If the oil is either on the ‘add’ line or below, be sure to top up!

How Can I Tell if my Oil is Dirty?

Your oil light coming on can also be a sign that your oil is dirty and requires changing. You may wonder how your perfectly clean oil manages to get dirty, but as you run your engine and the oil lubricates various parts, it can collect dust, dirt and other small particles that can over time build up and create gunk. So, while you may have more than enough oil to last you some time, this build-up of gunk can create blockages that cause your oil light to come on.

To find out if your oil is dirty, follow the same instructions as you would for checking oil levels manually. However, you will want to analyse the oil on the dipstick; any oil that is very dark in colour, has a strange odor or is thick and ‘gloopy’, it is a sign your oil is dirty and requires changing.

How Can I Tell if my Oil is Leaking?

Again, your oil light can come on if your oil is leaking. Upon examining your engine, you may not readily notice any leaks, however, if you leave your truck parked for a while on a level surface, and check back a few hours later, you should see puddles of oil on the ground if you have a leak. Perhaps you have not noticed any pooled oil underneath your truck when parked, but still have reason to believe you have a leak. It is not recommended that you mess too much with your engine, so you are always best taking it in to a diesel specialist to take a look.

Occasionally, an oil light can come on for no apparent reason; this is usually due to a faulty oil pressure sensor and can easily be replaced by your diesel specialist.

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