Switching to full synthetic on a semi-old car

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55
Location
AL
Hi, everyone. I recently purchased a 2007 Mercury Grand Marquis with the 4.6L V8 Triton/Modular engine. The car, as it sits right now, has 61,000 miles on it. To my knowledge, the car has only had dino oil ran in it all of these years. I've heard about switching to full synthetic on an older car can cause leaks around older gaskets. The car is completely dry underneath it, right now. No oil pan/valve cover seepage or signs of rear main leaking. Can I switch over to full synthetic on this car without worrying? I've been thinking about running a synthetic blend oil to try to slowly "break it in" for synthetic, so to speak. I don't know if that would make any difference. What do you guys think? TIA! :)
 
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58
Location
NEBRASKA
There can be an adjustment period any time an engine has been given a different oil, whether be a different brand, weight, or going to a synthetic. Sometimes leaks occur with poorly maintained engines, or consumption may increase, however the latter may be remedied withing a couple oil changes. This topic has been covered before. Use the oil of your choice within the manufacturers spec and monitor accordingly. I would not worry about switching to a synthetic.
 

Backwoods41695

Thread starter
Messages
55
Location
AL
There can be an adjustment period any time an engine has been given a different oil, whether be a different brand, weight, or going to a synthetic. Sometimes leaks occur with poorly maintained engines, or consumption may increase, however the latter may be remedied withing a couple oil changes. This topic has been covered before. Use the oil of your choice within the manufacturers spec and monitor accordingly. I would not worry about switching to a synthetic.
Thanks for the reply. I know that the previous owner that I bought it from said that he would go 5000 and sometimes 7000 miles on conventional oil, which honestly makes me cringe. I’m coming up on 3000 miles since the first oil change I did on the car and the oil I used was conventional again, and so far, it has not used any, but consumption starting after switching to synthetic is another concern of mine. I might just start out with synthetic blend and go from there.
 
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1,306
Location
PEARL River la
Conventional oil is a blend right now and has been for a while. You can go with Valvoline Advance Synthetic with Maxlife which is slightly higher viscosity. No worries about the low mileage as this can be run in new engine.
 
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295
Location
Maryland
If you are putting ~1000 miles a month on your Mercury Grand Marquis, you can easily go 5000 on an oil change without worries using most any brand of a conventional or synblend motor oil of appropriate weight that meets either the SN+ or SP ratings. Now if you are doing mainly short trips where the engine never really gets up to and maintains it's normal operating temperature, then you should follow the Severe Service maintenance recommendations for your car.
 
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35,248
Location
NY
I'd make the change. I'm not sure what you plan for an OCI, or how the vehicle is going to be driven. For the first synthetic oil run I'd probably do an oil and filter change after 5K miles. If for some reason it leaks you can always use a synthetic High Mileage Oil. It might do some additional cleaning and help with leaking seals.
 
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33
Location
Rockaway, NJ
One data point: I switched my Dad‘s 2006 Grand Marquis from convention to Mobil 1 5w20 without incident in fact I believe it drives/idles bette but no data to prove it.
Details: The switch occurred 6 years ago and he only drives 3k miles/year.
My 2 cents: Give it a try.
 
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6,756
Location
Wet side WA
I switched my Corolla over at 66,000 without issue but this car has very low miles for a car that old. Does the engine currently have any leaks? My Toyota knock on wood has no leaks at 141K miles, and barely any oil consumption between a cup and less than half a quart. Which I believe by the way is mostly NOACK difference.
 
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2,107
Location
South Carolina
Yes you can. I've done it to all of my old vehicles. No need to start with semi-syn. Like demarpaint said, do an early change on the first fill.
 
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316
Location
MO, USA
you can switch at any time to full synthetic early synthetics had esters which caused seal swelling leaks could occur. esters are not used in modern synthetics. you will need to change a little early as full syn will clean out your engine, a cheap filter would be a good idea to capture the gunk
 
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749
Location
Massachusetts
Well honestly, it may be an older car but at 61,000 miles the engine really isn’t. And that’s where the oil is going, so I’d just give it a go. I don’t even think I’d waste my time on semi-synthetic. Go full bore. Worst that happens is it leaks and you go back to conventional next time around and that legendary 4.6 lasts till 500,000 miles without much bother.

We all know the abuse those engines have gone through (and handled it). Synthetic oil will be a treat for that thing. Honestly, I used to work for a fleet...cop cars were on the menu. Those engines were the last thing we worried about in our fleet - and we had the 5.3 GM, the Chrysler 3.5 (actually every Chrysler engine they made, with the 2.7 being the worst). Every ford engine (honestly all of them were trouble free for the most part, except for the intakes on the Windstars). Every GM engine...the 3.4’s kept me busy every singe day, honestly. But the Ford 4.6?? The only thing I ever did to those things were alternators, spark plugs and DPFE sensors. That’s it. Idle all day long, pedal to the metal, used and abused. Bullet proof.
 
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1,600
Location
Caldwell Idaho
you can switch at any time to full synthetic early synthetics had esters which caused seal swelling leaks could occur. esters are not used in modern synthetics. you will need to change a little early as full syn will clean out your engine, a cheap filter would be a good idea to capture the gunk
O.K.
 
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4,559
Location
Decatur AL USA
Honestly 7,000 mi unless it's an ultra short tripper is unlikely to be an issue in a 4.6L 2V. It's pretty easy on oil. I think we have a member with 400,000 mi on 10,000 mi changes of SuperTech Synthetic. Might not be a bad idea to follow a proven combo it's cheap at like $14 for 5
qt or the Havoline DS Synthetic (Im told I recommend to often) at $18 per 6 qt box is a nice round number for many Fords.

If he was using the recommended 5W-20 they have basically all been blends anyway.
 

Backwoods41695

Thread starter
Messages
55
Location
AL
Honestly 7,000 mi unless it's an ultra short tripper is unlikely to be an issue in a 4.6L 2V. It's pretty easy on oil. I think we have a member with 400,000 mi on 10,000 mi changes of SuperTech Synthetic. Might not be a bad idea to follow a proven combo it's cheap at like $14 for 5
qt or the Havoline DS Synthetic (Im told I recommend to often) at $18 per 6 qt box is a nice round number for many Fords.

If he was using the recommended 5W-20 they have basically all been blends anyway.
Thanks for the replies, everyone. Here is a pic of the oil he was using. Is this a blend oil? I’m an OCD maniac and 5,000 miles is usually my cutoff point.
 

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Backwoods41695

Thread starter
Messages
55
Location
AL
Yes that is a blend. Good oil
That's good to hear. The engine seems to be in good shape. Has lots of power. And has not used any oil, as of yet. I bought this car just kind of as a toy. Weekend cruiser and a nice soft ride compared to my F-150 pickup that rides like a goat wagon. It's not going to see a terrible lot of driving.
 
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1,415
If you want to switch over to synthetic go ahead.. 5-7k is nothing most conventional oils these days are blends and the additive packs used in modern oils can handle it.. What's your want for synthetic.. You looking to do one oil change per year or run 10-15k oci?
 
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