<p>Reader Question

My 1993 Nissan 240Sx consumes a quart of oil every 600-700 miles; no leaks, no smoke. Do I need a new engine? If not, when do I start
worrying?

Bruce
Virginia

Hey there Bruce,

If you are absolutely positive that there are no external oil leaks I would suspect you have some internal engine wear going on which is consuming this missing engine oil. Rebuilding this engine does not make sense cost wise so I would try playing around with a few cheap options first and see what happens.

I can recommend the following:

1. Check to make sure the PCV system is working properly. The Positive Crankcase Ventilation system allows the engine to breath and vent off excess combustion gases. This system is usually regulated by a PCV valve (call the Nissan dealership parts department and ask them if your engine has a replacement or cleanable valve and where it it located) which should be cleaned or replaced over time. If this valve gets restricted or dirty it will cause excessive internal engine pressure which can put pressure on oil seals and o’rings and other internal oil sealing parts. If you are unsure how to check or replace this part have your local mechanic or a fast lube place check your PCV system for you to make sure there is no restriction.

2. Use a thicker weight of engine oil. I would assume you are using either 5w-30 or 10w-30 weight engine oil, which would normally be just fine. Using a thicker weight engine oil like straight 30 weight (Castrol makes a great straight 30 weight oil) will slow down internal engine oil consumption since this thicker oil is harder to seep through worn out internal oil seal. If you are currently using straight 30 weight you might be able to use straight 40 weight…although that is pretty thick oil for this little engine. In Houston were I am located it does not get cold enough to really do any harm, but you probably see snow in the winter months and this thick oil could get too thick during colder months and cause a lack of lubrication issue if not allowed to properly flow through the engine. The colder it is outside, the slower your engine oil is going to move throughout the engine.

3. Try a can of Engine Restore motor oil additive. You can buy this oil additive at any local auto supply store, it is in a shiny silver metal can. Just add a can of this to your clean engine oil and drive the car as normal. I have had good success with this additive with engines that consumed oil and or smoked from the tailpipe. It does not work overnight, but you should see a slow down in oil consumption over a 3,000 mile interval. You will need to add a can of this additive during each oil change.
Let me know how things work out.

Blessings,

Austin Davis

Reader Follow Up

Austin,

I’ve tried the second and third options already, but I’ll look at the PCV alternative. You’re right that an engine rebuild would cost more than the car is worth on the market ($2500 vs $1250), but it’s a convertible (only made for two years) and I’ve put in leather seats, K&N air filter, and repainted. Not really looking forward to getting rid of it.

Thanks, Bruce