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5-20 Motorcraft synthetic blend. 100% synthetic better?

2008 Expedition 48k

Would we save fuel by using 100% synthetic, such as Wal-Mart’s 5-quart jugs?

Would the cost difference be worth the fuel savings?

Less engine wear?

Driven gently but sometimes the vehicle is pushed hard performing emergency bloodeliveries.

Would the cost difference be worth the fuel savings?

The more accurate way to ask that question would be “What mpg increase will I need to get in order to pay for the extra cost of 100% synthetic?” You can get this answer with some simple math:

1: Determine the extra cost with 100% synthetic.

2: Determine how many gallons of gas you use between oil changes.
(ex: 5000 miles @20 mpg = 250 gallons)

3: Determine cost of fuel between oil changes.
(ex: 250 gal * $2.50/gal = $625.00)

4: Determine the mpg increase you would need to see to pay for the extra cost of 100% synthetic.
(ex: If the extra cost was $20, then your mpg would need to rise from 20 to 20.66 mpg, or 3%).

My guess is it would be tough to see the switch get you a 3% increase in mpg, but you should do the quick math to see what the figure is for your vehicle.

Will 100% synthetic result in less engine wear? In theory, perhaps. But if you change your oil according to the schedule in your owners manual, you will never be able to see the benefit from the decreased wear. (Maybe an engine part will wear out at 316,000 miles rather than 317,000 miles).

If you are going to use full synthetic, then go with the 0W-20. It will give you the least wear and best mileage. (0W-20 meets all Ford specs for 5W-20 blend.)

There would be no noticeable difference in fuel economy with same weight synthetic blend or full synthetic oil. No fuel savings with full synthetic, therefore no advantage on that front.

What is your planned oil change interval? If you plan to change the oil with the same interval, then no cost advantage to full synthetic.

I believe the advantage goes to full synthetic oil if you run a vehicle very hard, ie using it to tow a trailer frequently. The advantage goes to full synthetic in vehicles that are driven very few miles per year and mostly on short trips. In this case you could go with a yearly oil change vs every 6 months with vehicles driven less than 5K miles per year.

If you plan to keep the vehicle in service for 200+K miles before retiring it, then perhaps an advantage to full synthetic in less intermal engine wear. If your oil change interval is 5K miles and/or every 6 months there should be little difference in engine wear, if any at all.

From your described use I don’t think you’ll derive any cost savings using a full synthetic, a synthetic blend, or even conventional motor oil. If the “peace of mind” factor has you leaning toward full synthetic, then no issue with that; just don’t justify it as a costs savings since there really is none.

I won’t get into the cost effectiveness of synthetic oil, except to say that you will need to do some kind of financial analysis (like a break even analysis) to determine that for yourself. JoeMario has given you guidance in that area.

I will stick my neck out there and say there is no appreciable difference in fuel economy between synthetic oil and conventional oil. If there is a difference, it is small enough to be insignificant. Consequently, the difference in fuel economy between a synthetic blend and a full synthetic oil would be even less.

Synthetic oil is good for many things. For engines that require it, like those that operate at high temperatures and those that are turbo-charged, there is a definite benefit to using it. However, if your goal is to improve your fuel economy, the best things you can do are:

*Drive more efficiently
*Keep your car in shape
*Plan & combining trips
*Choose a more efficient vehicle

( source: )


I drive gently: -gentle accelerations and looking ahead and coasting to stopped traffic or red signals, etc.
-driving at 50 mph on highways and interstates to lower wind resistance.
-always combining trips, etc.
-air conditioning off
Unfortunately, it needs to be a big SUV to haul large medical equipment.

Are synthetic oils slipperier and create less internal engine drag?

For hospital medical emergencies, this vehicle has traveled at high speeds, up mountains, againstrong headwinds, all of which impose quite a load on the engine.
When arriving at the hospital we could smell a hot engine though we constantly glance at the temperature gauge and it is never even slightly above normal.

I doubt it. How about carefully measuring your mileage with regular oil, then when you change do the same.

I used to do that but gave up.
I try to be so gentle and fuel efficient. But when we have a red light and siren transport, it completely ruins our fuel mileage figures.
(We used a third of a tank on a 101 mile trip heading up the mountains against a strong headwind.)

Robert; on a previous post we argued that the reason for 0W20 and 5W20 was for Ford to meet the CAFE requirements, and get your engine to last just past the warranty expiration.

Your interest is to get the maximum life out of your engine and get acceptable gas mileage. Using 5W20 mineral oil and pushing your vehicle hard in a hot climate will cause significant loss of engine life.

My son bought a 2004 Mazda 3, which still had Ford’s idea of saving fuel by using 5W20 or 0W20 synthetic. He ignored the manual and has used 0W30 full synthetic for the last 70,000 miles, and the engine still runs like new and uses no oil.

If you go overseas to countries with no Fuel Efficiency standards, that same Mazda 3 will use 20W50!!! in a tropical country and 5W30 or 10W30 in most other countries.

You will be hard-pressed to identify ANY difference in gas mileage between 0W20 and 5W20.

Personally, I would use the 5W20 full synthetic till the warranty runs out and then switch to a 0W30 or 5W30 synthetic depending where you live. A 2% fuel savings over a 15 year period or 225,000 miles of driving (about $560 at today’s prices) will not buy you an engine rebuild!!! Similarly, the extra $30 per oil change for a high quality full synthetic costs $1125 over the life of your vehicle, about 20% of an engine overhaul at today’s prices.

Unfortunately, I am not qualified to answer your question about whether synthetic oil reduces friction, but I will answer anyway. One would really need to spend a lot of time reading this web site to answer that question and I am not curious enough to want to read it all.

The main benefit of synthetic oil is that it can hold up exposure to high temperatures. Your vehicle is naturally aspirated and has a liquid cooling system (as opposed to having a turbo charger or being air cooled), so this benefit is pretty much lost on your vehicle.

There might be some benefit, but I doubt it would be enough to notice a change in your fuel bills.

The argument that your engine will fail right after the warranty period is pure fantasy. My Mustang has about 95k on the clock with a supercharger and it’s seen nothing but 5W-20 it’s entire life. Likewise my brother has F-150 with the 4.6L that has about 170k miles on it, and it still runs as good as new. My grandparents all have Crown Vics/Grand Marquis that spec 5W-20 oil, and shockingly the cars are still on the road.

The 5W-20 / 0W-20 oil has been discussed at length on the Bob’s The Oil Guy and the determination is that the stuff is as good as or equal to 5W-30/10W-30 in just about every way.