Oil change interval: conventional vs synthetic

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31
Location
NJ, USA
First, I have never worked on cars before (am 48 years old) but will start doing oil changes. I bought this summer a '95 Land Rover Defender which has a 3.9L V8 1960s design Buick derived engine with a relatively new engine with 26K miles (83K miles on the chassis). On the Defender forums, the thought is if an engine has been maintained on conventional/diesel (Rotella) oils, don't change to synthetic as this may encourage leaks. OTOH, if only synthetics have been used (as in my case), then continuing is OK. The Defender Source forum members by and large recommend 3000 mile oil change intervals with conventional oils. Since I am using Mobil 1 Synthetic, am I wasting $$ unnecessarily by changing every 3K miles. Should I lengthen the intervals between oil changes to 5K or more or is the case that it doesn't matter what type of oil is used and 3K should be the interval no matter what? I'm using a larger capacity Wix filter and will be installing the No Spill system to make oil changes more easily. Diff Lock
 
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40,838
Location
Great Lakes
Originally Posted By: ymc226
Since I am using Mobil 1 Synthetic, am I wasting $$ unnecessarily by changing every 3K miles. Should I lengthen the intervals between oil changes to 5K or more
Describe your driving patterns for this vehicle. How long (in terms of time) does it take you to hit 5K miles? Do you do any short tripping? Extended idling?
 
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5,529
Location
Florida
What matter more in the driving style / conditions that the car will be in. For all we know, you could go 15k on Mobil 1 without any issues... Just saying, we need more info to make an educated recommendation. Or do you want us to blindly recommend an interval to you based on... NOTHING???
 

ymc226

Thread starter
Messages
31
Location
NJ, USA
Thanks for the quick replies. Since the truck is not galvanized, I parked it for the winter but drive it almost daily from April to November to and from work 20 miles each way in local moderate traffic conditions. Some stop and go but mostly local under 60 MPH. Since it is a 5 speed manual, I usually limit the revs to under 4K but keep it around 2.0-2.5K on the tach. I live in Central NJ.
 
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19,528
Location
Lake Forest, CA
Your driving is easy on oil, change oil&filter once a year with any name brand synthetic after the last drive in November when you park your car for 5 months.
 

ymc226

Thread starter
Messages
31
Location
NJ, USA
That's great to hear that I don't have to change every 3K. This summer is the first year I've had the truck and I put just under 7K on it from around July to the end of November (this is with it being in the shop for about 6 weeks total for repairs and restoration/waiting for parts or some mechanic to get to it) so I'd figure about 10K miles per year.
 
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444
Location
Switzerland
ymc226,
Originally Posted By: ymc226
That's great to hear that I don't have to change every 3K. [...]
I am not living in US, but I guess you might have heard about this one: http://en.wikipedia.org/wiki/3,000_mile_myth In Europe we normally have oil change intervals between 15000 and 30000 km on either 1 or 2 year basis.
 
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