Driving with no oil cap is not an ideal situation to be in. Nonetheless, these things happen. But how long can you drive without an oil cap if you are in this predicament?
To be blunt, you won’t get very far without an oil cap, and it would be better to arrange a temporary fix and then seek a new cap. I mean to start with, it’s pretty difficult to lose an oil cap; the only reason you would remove it is to fill the engine with oil. In which case, place the oil cap somewhere it can’t be lost. On top of the scuttle tray (wiper tray under the windshield) might seem like a great idea, but if you forget to put it back and drive up the road as soon as the wind catches it, it might be lost forever.
If it falls into the engine bay compartment, it will still be retrievable; it’s got to come out the way it went in, right? So, on top of the engine block next to the oil filler neck would be a better idea; at least somewhere in eye view where it will be difficult to forget to put it back. But lets say it’s already too late. It’s lost; well, you better read on.
Can you drive without an oil cap?
Yes, technically you could drive without an engine oil cap; the engine will not shut off or cause problems because the cap is missing. There aren’t any cars on the market that have sensors to determine that the cap is there. However, driving without an oil cap will lead to problems because it is there to keep the engine oil inside the engine.
How long can you drive without an oil cap?
Realistically, you could probably drive about a mile or two without an oil cap, and the only issue you’ll experience is a giant mess under the engine bay! Or if the engine was running at a standstill, expect to start noticing an issue after 10 minutes. The problem isn’t that you’re driving without a cap on for this very short distance, it’s just the cap’s job is to keep the oil inside the engine. So, expect that oil to spit out.
Driving further than a handful of miles you can expect more serious problems than a mess to clear up to start being present.
What happens if you drive without an oil cap?
Driving without an oil cap is problematic for a number of reasons:
First, it would lead to driving low on oil. Driving with very little or no oil in the engine would cause the engine to become dry, and the rotating components would eventually seize without any lubrication.
Secondly, the cap stops the oil from being thrown out of the top of the engine. As we’ve already pointed out, the oil has only one place to go with no plug at the top. And let me tell you, the mess oil makes, the smell and smoke pouring out everywhere as it leaks onto a hot engine, is just a nightmare to clean up. Not only that, but it can also damage electrical components if the oil gets into them, which will most likely then result in the engine misfiring.
Thirdly, dirt and debris can get into the engine without an oil cap. Debris will make light work of destroying an engine, even if there is still plenty of oil.
It is all doom and gloom, but it isn’t worth the hassle of driving a car without an oil cap. Instead, you can use lots of household items as temporary replacements.
What to use instead of an oil cap?
Before you read further, whatever you use instead of an oil cap is a temporary solution.
One thing to note is no matter what you use, it must be a larger diameter than the oil cap hole and not of a material that could be sucked into the engine. Trying to block the hole with some scrunched newspaper would be disastrous.
It isn’t easy to tape anything to an engine, but you may be able to duct tape something like the top of an old tin can. You can be creative here; an old shoe, anything you may have lying around in the car, might work very temporarily to stop the oil being thrown from the top of the engine.
You could use an old rag, some cable ties, and duct tape as a last resort or in an emergency. Cable tie a bit of the old rag around the outside of the oil cap filler neck, then duct tape it down. As pointed out earlier, there is a risk the rag could get sucked into the engine, so I wouldn’t recommend doing this unless there was no other option. You need to ensure the rag won’t just fall off as soon as you start the engine, so make sure it’s secure.
When using a temporary oil cap solution, you must avoid driving the vehicle hard, keep the RPMs down to the minimum, or you risk dislodging the makeshift cap and causing a problem.
Engine oil caps are relatively unique to each vehicle brand, so the cap from a BMW probably won’t fit on a Peugeot. This might mean you need to seek a dealership to get a replacement. Although, some auto parts stores may stock an aftermarket branded version. So once your temporary repairs have been done, that’s probably the only place you want to drive if you have to. Equally, a local mechanic may have the one you need lying around.
Driving without an oil cap is not recommended; try using a temporary repair and getting a replacement as soon as possible is a much better idea. Even better than that, don’t drive if you can help it and get a replacement as soon as you identify yours is missing. It’s pretty difficult to lose your cap but to answer the question, how long can you drive without an oil cap? Only a mile or two, or with the engine running for no more than about 10 minutes.