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Sinister Manufacturing Co. Inc. offers automotive retail services.

BBB Accreditation

A BBB Accredited Business since

BBB has determined that Sinister Manufacturing Co. Inc. meets BBB accreditation standards, which include a commitment to make a good faith effort to resolve any consumer complaints. BBB Accredited Businesses pay a fee for accreditation review/monitoring and for support of BBB services to the public.

BBB accreditation does not mean that the business' products or services have been evaluated or endorsed by BBB, or that BBB has made a determination as to the business' product quality or competency in performing services.

Reason for Rating

BBB rating is based on 13 factors. Get the details about the factors considered.

Factors that raised the rating for Sinister Manufacturing Co. Inc. include:

  • Length of time business has been operating
  • Complaint volume filed with BBB for business of this size
  • Response to 3 complaint(s) filed against business
  • Resolution of complaint(s) filed against business

Customer Complaints Summary Read complaint details

3 complaints closed with BBB in last 3 years | 1 closed in last 12 months
Complaint Type Total Closed Complaints
Advertising/Sales Issues 0
Billing/Collection Issues 0
Delivery Issues 0
Guarantee/Warranty Issues 1
Problems with Product/Service 2
Total Closed Complaints 3

Customer Reviews Summary Read customer reviews

1 Customer Review on Sinister Manufacturing Co. Inc.
Customer Experience Total Customer Reviews
Positive Experience 0
Neutral Experience 0
Negative Experience 1
Total Customer Reviews 1

Additional Information

BBB file opened: August 30, 2010 Business started: 01/01/2004 in CA Business incorporated 04/18/2011 in CA
Type of Entity


Business Management
Ms. Rosa Guitierrez, Manager Mr. Brian George, President Andrew Socol, Director of Marketing
Contact Information
Principal: Ms. Rosa Guitierrez, Manager
Business Category

Auto Parts & Supplies - New

Alternate Business Names
MKM Customs
Products & Services

Sinister Manufacturing Co Inc offers Ford, Chevy, GMC, and Dodge diesel performance parts.

Customer Review Rating plus BBB Rating Summary

Sinister Manufacturing Co. Inc. has received 0 out of 5 stars based on 0 Customer Reviews and a BBB Rating of A+.

BBB Customer Review Rating plus BBB Rating Overview

Additional Locations

  • 2025 Opportunity Dr Ste 7

    Roseville, CA 95678 (877) 692-4110 (916) 772-9253


BBB Customer Review Rating plus BBB Rating Overview

BBB Customer Reviews Rating represents the customers opinions of the business. The Customer Review Rating is based on the number of positive, neutral and negative customer reviews posted that are calculated to produce a score.

Customer Review Experience Value
Positive Review 5 points per review
Neutral Review 3 points per review
Negative Review 1 point per review

BBB letter grades represent the BBB's opinion of the business. The BBB grade is based on BBB file information about the business. In some cases, a business' grade may be lowered if the BBB does not have sufficient information about the business despite BBB requests for that information from the business.

BBB Letter Grade Scale

BBB Rating Value
A+ 5
A 4.66
A- 4.33
B+ 4
B 3.66
B- 3.33
C+ 3
C 2.66
C- 2.33
D+ 2
D 1.66
D- 1.33
F 1
NR -----
Star Rating scale

  Average Score
5 stars 5.00
4.5 stars 4.50-4.99
4 stars 4.00-4.49
3.5 stars 3.50-3.99
3 stars 3.00-3.49
2.5 stars 2.50-2.99
2 stars 2.00-2.49
1.5 stars 1.50-1.99
1 star 0-1.49

BBB Customer Review Rating plus BBB Rating is not a guarantee of a business' reliability or performance, and BBB recommends that consumers consider a business' BBB Rating and Customer Review Rating in addition to all other available information about the business. If the BBB Rating is NR then only Customer Reviews are used for the Star Rating.

Complaint Detail(s)

3/2/2016 Guarantee/Warranty Issues | Read Complaint Details

Additional Notes

Complaint: I purchased a Turbo from this company in May or this year, it was installed in the Fall by the lead Diesel mechanic at my local ford dealer. The turbo failed in less than 200 miles, I called the company to report the issue to the business and was transferred to the warranty dept. Which was less than helpful with addressing my concern than giving me life advice on how I was reporting my problem. I called back and spoke with the Sales account Manager ****** ********** and after detailing the issues I was having along with emailing photos of the defective turbo and what had happen to it, he ****** ********** first said they would try to warranty it but that could take 8 weeks or longer, I told him I couldn't wait that long that I needed my truck working on the road again. At this point I purchased a replacement Turbo from another company based off the projected length to get my truck working again. The next email From ****** ********** advised they would replace the defective Turbo with a new one, my reply was to explain what I just stated, I had already purchased a new Turbo to get my truck back on the road. At this point I was promised a Full Refund my ****** ********** and all I had to do was return the defective turbo to them. I agreed and they emailed me a UPS return label to send the turbo back, I was advised that as soon as they could see I had shipped the Turbo I would receive my refund of $1,500 and change and the matter would be closed. I complied and sent the turbo back. Also I ask to return another item I had purchased from them and they gave me an RMA# for that item as well and returned it. I have not received the refund I was promised or the refund for the RMA# item I sent back to this company. When I called to ask where it was I was given excuses and then advised the turbo was being looked at by the companies warranty dept, the same department that was less than helpful when I called the first time.After a week or so, the refund was changed to a store credit. then no contact.

Desired Settlement: I was promised a refund by the sales manager of this business, with the understanding all I needed to do was return this item to them with the shipping label they provided, I did, I want them to honor that refund!It was promised verbally in a phone call, and confirmed in emails. I also want the refund for the fuel sump I returned to them. I am out of pocket over $2000+ due to this item being defective and the repairs it took to replace it. Just a refund, no store credit. thank you

Business Response: Tell us why here...

In short, a refund could not be given to the customer (***** ******) due to the condition of the turbo in which it was received. The RMA was issued with the understanding this turbo was damaged due to MFG. defect, this would approve a RMA,  even though this item is listed  on our website as a  "no warranty/returnable item, due to the fact of it being a high performance item. Again, as it is listed on our website: (Seen Below)


Upon receiving the turbo and it being inspected by our warranty department. The turbo was not damaged or failed due to mfg. defect, but a foreign object in the turbo or improper installation of the turbo. This was concluded by the type pf damaged that was visible on the turbo upon delivery. The damage was from a foreign object that was introduced to the turbo or improper installation. This will not be accepted as a return under warranty for "mfg. defect" and no refund can be issued to the customer. 

At this point the customer was notified on the current status of this return. A compromise was offered to the customer, but without a answer from the customer with the options were giving. The turbo was sent back to the customer and RMA was closed.

Consumer Response:

I am rejecting this response because: This is not accurate, I purchased the Turbo through **** not the company website, if you call this company and get placed on hold, you will hear a recorded message stating that Sinister Diesel stands behind everything they sell! I guess this only means until you have an issue with an item they sell! This turbo is supplied to Sinister Diesel by ****** and ****** warranties it!! To restate, I was promised a refund by s CEO there! No conditions, I emails to confirm this, along with pics of the condition of the Turbo. I sent this all to the company and was promised a refund. This turned out to a misdirection on the companies part, the RMA they speak of was not even issued for the Turbo, but second part I purchased from them, a Fuel Sum kit which I have not received a refund for! So to be clear, I was promised a refund for the Turbo based on it failing, and the RMA was issued for the fuel sum, and I have received neither to date. I have all emails saved from this company to show my side of this to be accurate.My last issue is the mention of my not responding, I did respond to every email, and again I have them saved, the other issues is the return of this defective turbo, I have not received it! Please all I am asking is for this company to stand by what they promised! I spent thousands of dollars with them with the understanding they stand behind what they sell and make a quality product,!

Consumer Response: I am rejecting this response because: If it was sent back to my residence, some one has defiantly taken it, I'll be waiting to hear more on how this progresses, please advise as soon as you can

Business Response: *** has ended their claim and a credit will issued back to the customer (***** ******) attached is a credit memo that has been issued back to the customer.

8/7/2015 Problems with Product/Service | Read Complaint Details

Additional Notes

Complaint: Sinister Diesel's 6.0 Y pipe with a lifetime warranty was purchased and installed in October 2014. Beginning of June 2015, the product is defective. Request for complete refund is denied. Only options given by Sinister are return of defective product for evaluation and replacement, at their discretion, or purchase new product, return defective product for evaluation and refund of money, at their discretion, for new product. I do not want a replacement, because I do not want to deal with this again. I want a refund so I can buy a better product.

Desired Settlement: Send me a full refund or send me a 6.0 Powerstroke MBRP Y pipe.

Business Response:

Unfortunately, the item Mr. ***** ordered is a high performance item, meaning it is used for "off road" or "race use only," which is noted on the product's disclaimer. We have given Mr. ***** a couple options to get the matter resolved. Should a race part fail due to a defect in manufacturing as determined by Sinister Diesel, customer is entitled to replacement of that specific part. Unfortunately, due to the extreme conditions that these parts are exposed to we cannot issue a refund. By installing this product onto the vehicle, buyer assumes all risk and liability associated with its use. At this point, we can provide a prepaid UPS return label. Once received, we can inspect and test the product for any manufacture defects. In hopes of resolving this matter with the customer, we will be more than happy to send out a replacement.



Thank you,

Rosa McElroy

Wholesale Account Manager

2025 Opportunity Drive

Roseville, CA 95678

P: 877-692-4110

F: 916-772-9254

Consumer Response: I am rejecting this response because: Wether the item in question is intended for "off road use only" or is a "high performance" product, a failure in a very short span of time is unacceptable. The product couldn't even be used in any of the intended applications, because it failed well before it could be. I expressed that replacement was not an option, because I do not want another faulty product, and that full refund is the only way I will be satisfied.

Business Response:

Sinister Diesel stands behind their products 100%. Our products do include a “lifetime warranty”. The product that was purchased is intended for “off-road use only.” By installing this product onto the vehicle, the buyer assumes all risk and liability associated with its use. In this situation, the customer did not want to allow us to do our part and inspect the item first, just demanded a refund for their money. Since the item has been installed, unfortunately we cannot offer a refund. We are more than willing to inspect the item and ensure the item is replaced.


Thank you,

**** ******* ********* ******* ******* **** *********** ***** ********** ** ***** ** ************ ** ************

Consumer Response: I am rejecting this response because:  Sinister wanted me to remove the part from my truck, which in turn puts the truck out of commision, to return it for inspection. When the truck needs to be in service, this is an unacceptable option. The other option I was given, was to purchase a second part, install it and send the defective one back for inspection hoping my money will be returned for the second purchase. This is also an unacceptable solution because $500 is a lot of money to be out of pocket, hoping that it will be returned. I offered for Sinister to send me a replacement item from a different manufacturer, for whom they are a dealer for, because I did not want another item manufactured by Sinister. This offer was declined by Sinister. 
    In summary, I asked for a full refund, or a replacement with another product. 

9/17/2014 Problems with Product/Service | Read Complaint Details

Additional Notes

Complaint: Purchased a Turbo to replace my factory one back in January 2014. Upon receiving the turbo and having it installed the product did not perform as described and did not operate like it was supposed to. Had a diesel shop look at my truck and everything was working and they could not understand why the turbo was not operating as it should, the shop finally determined that it was a faulty turbo sent to me since other trucks were running the same set up i was and theirs operated fine. After spending more money on getting tunes for the turbo and dealing with other shops, the product still did not operate as it was supposed to. After finally getting ahold of *** ******* i spoke with the manager and he could not understand why the product was doing that, I was told that he would get back to me and he never did with any information on what they could do. Highly unsatisfied with the product and the customer service. Have spent the last 8 months trying to resolve this and have gotten nowhere. The product was $2000.00 and it does not work.

Desired Settlement: Im not looking for a refund but would like my product exchanged for the same product but one that operates as it is supposed to. Do not wanna be swindled out of my $2000.00 for their product. Again all I'm asking for is a exchange.

Business Response: Hello,

Thank you for bringing this complaint to our attention. The product purchased was an after-market performance auto part and does not have a warranty option available because it's a race product, which is stated on our website. The turbo was ordered online where specific terms & conditions have to be acknowledge before buying this particular racing part. The terms and conditions were acknowledged and agreed to by the customer.

We first attempted to work with the customer to resolve their concerns when they contacted us after it was installed in their truck for four months. We provided technical assistance and free product tunes. After no resolve for the customer a return was requested per the customer. An explanation to the customer for the denial of the return was due to the fact that the product purchased is "intended for race use only"

In hopes to resolve this with the customer we are looking to get a replacement part out tomorrow, 9/11/14.

Consumer Response:  
Better Business Bureau:

I have reviewed the response made by the business in reference to my concern, and find that this resolution is satisfactory to me.

Customer Review(s)

The customer review(s) below are un-filtered. These positive and negative reviews are not used in the calculation of the BBB Rating. If you wish to file a complaint and request a resolution to your issue please click here. This customer review section is not BBBs complaint resolution system. Customer Reviews are the subjective opinion of the individual who posted the review and not of Better Business Bureau. A customer review is not posted on a business if a BBB complaint on the same issue(s) is also filed. BBB cannot guarantee the accuracy of any customer review and is not responsible for the content of any customer review. Public comments are not customer reviews.

Customer Reviews Summary

1 Customer Review on Sinister Manufacturing Co. Inc.
Positive Experience (0 reviews)
Neutral Experience (0 reviews)
Fusion Chart
Fusion Chart