High Mileage vs Full Synthetic Oil

Article by Mark Trotta

All my classic cars and vintage motorcycles use conventional oil, but on my "fleet" of daily drivers (mine, wife's, kids) I use either synthetic-blend high mileage or full synthetic.

high mileage vs full synthetic oil

Current statistics show that nearly half of all cars, trucks, and SUV's use synthetic blend or full synthetic oil. So which one is better? The short answer is full synthetic is always better, but cost is the main reason why I buy high mileage oil vs synthetic oil.

If you have over 75,000 miles on your modern car or truck, consider switching to a high-mileage motor oil. They feature a blend of synthetic and mineral-based oils with extra detergents added to them. The detergents help remove any sludge build-up that an old or high mileage engine may have, and also helps keep them clean internally. Most high mileage oils also have seal conditioners to help stop and prevent oil leaks, although results are probably marginal at best.

Best High Mileage Motor Oil

There's lots of good oil brands out there - my favorites include Castrol, Pennzoil, and Valvoline. Truth is, the brand really doesn't matter much, as long as it meets the standards specified by the manufacturer (which all name brand oils do). Once I had brand loyalty, but now I let price be the deciding factor as to which oil I buy.

Valvoline MaxLife Oil

Valvoline claims they were the first company to market a high mileage motor oil. Their high mileage MaxLife is designed to remove sludge and deposits from your engine. It also contains anti-oxidants that help prevent oil breakdown, which in turn prevents sludge and deposit formation.

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Shop: Valvoline High Mileage Oil

I often purchase MaxLife Motor Oil for my 2008 Ford Sport Trac, which currently has 160,000 miles. The recommended interval for this vehicle is 7,000 miles, but I usually change the oil and filter at 5,000 miles.

Castrol GTX High Mileage Oil

Back in the eighties, I used Castrol GTX in my old muscle cars, so I like the brand. Castrol GTX High Mileage Oil is formulated to be less phosphorus than other synthetic blend oils.

high mileage vs full synthetic oil

Shop: Castrol GTX High Mileage Oil

We often select Castrol GTX High Mileage for our daughter's 2008 Chevy Cobalt, which currently has 105,000 miles. Recommended oil change interval is 5,000 miles.

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As a third choice, I frequently buy Pennzoil High Mileage Oil when it's on sale.

Full Synthetic Oil Benefits

If your vehicle sees wintery-cold start ups, brutal-hot summer driving, or daily stop-and-go traffic, you should be putting full synthetic oil in your crankcase. Even if your car or truck doesn't see these extreme driving conditions, it will still benefit from full synthetic oil, just not as much.

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If used over the course of many years, full synthetic oil will increase the lifespan of your engine. It provides greater resistance to oxidation than do mineral-based oils.

Are All Synthetic Oils The Same?

Well, yes and no.

Oil companies spend untold amounts of money on advertising, trying to convince you that their brand is the best. But for the average user who's not competing in racing events, any synthetic oil is just as good as any other. The fact that they all pass the same API certifications tells you alot - they're all great for a daily driver car or truck.

Castrol Edge Full Synthetic Oil

This is Castrol’s most advanced engine oil. They claim their Edge full synthetic oil is three times stronger against viscosity breakdown than other full synthetic brands.

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Shop: Castrol EDGE Full Synthetic Motor Oil

Not only is Castrol Edge recommended by many automotive manufacturers, it's also recommended for BMW and Triumph motorcycles as well.

Pennzoil Full Synthetic Oil

Pennzoil Ultra Platinum oil exceeds car manufacturer requirements for cleanliness and protection (ILSAC GF-6, Dexos1 and Ferrari approvals). It is suitable for all car, truck, and SUV gasoline and turbocharged engines.

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Shop: Pennzoil Ultra Platinum Full Synthetic Motor Oil

I've been using full synthetic in our 2013 Ford Edge for the last 95,000 miles. Oil change interval is 8,000 miles.

Every now and then, I'll buy Mobil One synthetic when I find it on sale.

Oil Changes Are Still #1 Priority

Oil changes are the most important part of vehicle maintenance. Air filters and fuel filters are also important, but not nearly as much. For example, if you drive around with a dirty air filter or dirty gas filter, the worst that could happen is you lose performance. If you drive around with dirty oil for too long, you put your engine at risk of expensive internal damage.

high mileage vs full synthetic oil

Ordering Online

I often take trips to the local parts store, but when my schedule gets tight (regular job and side work) ordering motor oil online frees up some of my valuable time. If I order it a week before I need it, delivery time is less of a priority. Plus, it's a little less expensive, and there's no driving or waiting on line.

Notes and Misc

  • You can switch back and forth between oil types, you motor doesn't care.
  • Any brand of new oil is better than dirty old oil.
  • Change your oil at recommended intervals. Oil is cheap, engines aren't.
high mileage vs full synthetic oil

TIP: I find that five-quart oil containers are easier and quicker to pour, plus you can put the old dirty oil right back into them for easy disposal.


I have rebuilt many automotive and motorcycle engines, and have seen first-hand the damage caused by lack of regular oil changes. Once an old car's engine is sludged up, there is no easy way to clean it. You can try an engine flush, but these have very strong detergents which sometimes do more harm than good. So, if your engine oil comes out dark and sludgy, cut your mileage interval in half for the next oil change.


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